Shock excited far-infrared molecular emission around T Tau

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复旦大学生物医学研究院科学家首次发现人体生理状态下存在大量非细胞核蛋白的乙酰化修饰

癌细胞的增殖为方向。
法、意科学家揭示细菌低温存活之谜德、据中国军网２１００年１月１日援引新华社巴黎１１７月６
日电，国国家科研中心、法意大利卡梅里诺大学和德国杜塞尔多夫大学的研究人员通过合作研究发现，一种名为“ 冷休
皮层区域。“ 这说明人们在听到别人正面评价的时候非常关注自我。也就是说，如果家长和教师多夸奖和表扬孩子，将会十分有利于孩子形成积极的自我概念。如果领导也这样对待下属，将会十分有利于激发下属的的积极性。 ” 潘晓红也对实验对象进行了绩效反馈实验。结果显示，
饰特性与各种疾病的关系，指导相关药物的有效开发。
中科院上海生命科学研究院科学家
揭秘ＤＡ甲基化发生机制Ｎ
克蛋白” 的信使核糖核酸具有感知冷暖的特殊能力，使其只
有在低温时才会表现稳定，就是说，低温下这种信使核也在糖核酸反而能更有效地复制细菌的遗传信息，助细菌繁帮衍。长期以来，冷休克蛋白” “ 帮助细菌在低温下生存的机
癫痫是一种较常见的神经疾病，发病者占人口的Ｉ％左右，通常认为癫痫由神经细胞异常兴奋所致，具体病因尚但未完全清楚，也未有根本的治疗方法。日美科学家的研究结果有望为癫痫的治疗研究打开新的思路。该项研究的相关论文发表于美国《国家科学院学报》网络版上。
ＤＡ甲基化具有不可或缺的作用，且辅助因子能与组蛋Ｎ而白Ｈ发生相互作用并引发起始性的ＤＡ甲基化。这一研］Ｎ究首次从功能上揭示了组蛋白Ｈ３与ＤＡ甲基化之间的联Ｎ系，加深了对ＤＡ甲基化发生机制的认识。Ｎ

LettertotheEditor-Springer

Astron.Astrophys.322,L33–L36(1997)ASTRONOMYANDASTROPHYSICS Letter to the EditorDetection of[O I]63µm in absorption toward Sgr B2J.-P.Baluteau1,P.Cox2,J.Cernicharo3,D.P´e quignot4,E.Caux5,T.Lim6,B.Swinyard7,G.White8,M.Kessler9,T.Prusti9, M.Barlow10,P.E.Clegg8,R.J.Emery7,I.Furniss10,W.Glencross10,C.Gry1,6,M.Joubert1,R.Liseau11,B.Nisini11,P. Saraceno11,G.Serra5,C.Armand6,M.Burgdorf6,A.DiGiorgio6,S.Molinari6,M.Price6,D.Texier6,S.Sidher6,and N.Trams61Laboratoire d’Astronomie Spatiale,LP CNRS,BP8,F-13376Marseille Cedex12,France2Institut d’Astrophysique Spatiale,Bˆa t.120,Universit´e Paris XI,F-91405Orsay Cedex,France3CSIC.IEM.Dpto.Fisica Molecular,Serrano123,E-28006Madrid,Spain&OAN,Ap1143,E-28800A.de Henares,Spain4DAEC,Observatoire de Paris–Meudon,F-92195Meudon Cedex,France5Centre d’Etude Spatiale des Rayonnements,CESR/CNRS-UPS,BP4346,F-31028Toulouse Cedex04,France6The LWS Instrument Dedicated Team,ISO Science Operations Centre,PO Box50727,E-28080Madrid,Spain7Rutherford Appleton Lab.,Chilton,Didcot,Oxon OX110QX,UK8Queen Mary and Westﬁeld College,University of London,Mile End Road,London E14NS,UK9ISO Science Operations Centre,Astrophysics Division of ESA,PO Box50727,E-28080Madrid,Spain10Department of Physics and Astronomy,University College London,Gower Street,London WC1E6BT,UK11CNR-Instituto di Fisica dello Spazio Interplanetario,Casella Postale27,I-00044Frascati,ItalyReceived17December1996/Accepted9January1997Abstract.A high signal-to-noise52–90µm spectrum is pre-sented for the central part of the Sagittarius B2complex.The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory(ISO).The[O I]63µm line is detected in absorption even at the grating spectral resolu-tion of0.29µm.A lower limit for the column density of atomic oxygen of the order of1019cm−2is derived.This implies that more than40%of the interstellar oxygen must be in atomic form along the line of sight toward the Sgr B2molecular cloud. Key words:ISM:abundances–(ISM:)dust,extinction–(ISM:) H II regions–ISM:individual objects:Sgr B2–Infrared:ISM: continuum–Infrared:ISM:lines and bands1.IntroductionThe main form in which oxygen,the third most abundant ele-ment in the Universe,is present in the cold component of the interstellar medium remains one of the major unresolved issues Send offprint requests to:J.–P.Baluteau(**********************)Based on observations with ISO,an ESA project with instruments funded by ESA Member States(especially the PI countries:France, Germany,the Netherlands and the United Kingdom)and with the par-ticipation of ISAS and NASA of astrochemistry.Oxygen is supposed to reside mostly in the gas phase of molecular clouds,presumably as atomic oxygen or simple molecules,such as O2,CO,H2O and OH.Depletion of oxygen onto dust grains is not expected to exceed∼25%(van Dishoeck et al.1993)most of the oxygen being incorporated into silicate grains.This estimate does not include the solid CO2 which is found to be ubiquitous in the interstellar medium(de Graauw et al.1996)or the solid O2which may be an important grain mantle constituent(Ehrenfreund et al.1992).From chemical models the atomic oxygen is expected to account for10–30%of the gas-phase oxygen within molecular clouds(e.g.Bergin et al.1995and references therein).Although the abundance of O2in dark clouds is predicted to be similar to that of atomic oxygen(Black&Smith1984),the search for this molecule has so far been unsuccessful.The best limit has been obtained toward extragalactic dense molecular clouds by Combes&Wiklind(1995)who report an upper limit on the O2/CO abundance ratio of1.410−2,more than an order of magnitude lower than what is predicted by chemical models. Among other O-bearing molecules,the most commonly ob-served is CO which only contains∼10%of the total oxygen abundance(Lacy et al.1994).Recent estimates of the gas-phase H2O abundance which are based on ISO results indicate that water vapour can account for only a few percent of the total oxygen abundance(van Dishoeck&Helmich1996,Cernicharo et al.1997).Finally,the OH fractional abundance is even smallerL34J.-P.Baluteau et al.:[O I]in absorption toward SagittariusB2Fig.1.The LWS grating spectrum of Sgr B2from52to90µm.This spectrum was taken atα1950=17h44m12.0s,δ1950=−28o22 12 .The insert displays the line to continuum ratioaround the[O I]63µm line which is seen inabsorptionwith OH/O less than0.7%(Viscuso et al.1985).In conclusion,none of the above molecules can account for the bulk of thegas-phase oxygen.Recent observations have suggested that in the interstellarmedium most of the gas-phase oxygen might be in atomic form.Aﬁrst suggestion was made by Schulz et al.(1991)in order tointerpret their HDO observations.From HST ultraviolet spec-troscopy,Soﬁa et al.(1994)derived in two molecular clouds[O]/[H]values as high as1/3of the cosmic abundance of oxy-gen.Poglitsch et al.(1996)reported a possible detection of the[O I]63µmﬁne structure line in absorption toward DR21.They derived a relative abundance of atomic oxygen[O]/[H]∼6×10−4,implying that,in the foreground absorbing cloud,most of the oxygen is in atomic form.In this Letter,we report the detection of[O I]63µm in ab-sorption toward the main core of Sgr B2,a highly obscured H IIregion complex close to the galactic center.The data are basedon grating spectra obtained with the Long Wavelength Spec-trometer(LWS)on board of ISO.They provide aﬁrst estimateof the atomic oxygen content along the line of sight to Sgr B2.Higher spectral resolution data of the[O I]63µm taken withthe LWS Fabry-Perot will be published as part of a general ISOstudy of[O I]absorption in molecular clouds by Phillips et al.(1997).2.Observations and resultsFull LWS grating scans from43to196µm were obtained to-ward Sgr B2during Revolution287(30August1996)usingAOT L01as part of the ISO guaranteed time program ISM V.The LWS capabilities and the calibration procedure are de-scribed by Clegg et al.(1996)and Swinyard et al.(1996),re-spectively.Sixteen full grating scans were taken with0.5sec in-tegration time per grating step.The spectra were sampled at1/4of the spectral resolution element,being0.29µm for the short-wavelength detectors.The total on-target time was3047sec.The data have been processed through the LWS Pipeline Ver-sion6.0.Fig.1displays the spectrum between52and90µm ob-tained toward Sgr B2after combining the results of detectorsSW2to SW5.Small scaling factors(a few%)have been appliedto the individual spectra so that they join smoothly.The spec-trum consists of a strong dust continuum(at80µm,theﬂuxdensity is34,000Jy)with a series of lines all seen in absorp-tion.The signal-to-noise ratio being very high(∼200)most ofthe features seen in Fig.1are probably real.The OH absorptionlines which are labelled in Fig.1will be discussed in a forth-coming paper.A major aspect of the Sgr B2spectrum is thepresence of the[O I]63µm line which is seen in absorption-see insert in Fig.1.The absorption-line depth is3.0±0.5%at the LWS grating resolution.A further important point is theabsence of emission in the[O III]88µm and[N III]57µmatomicﬁne structure lines normally detected toward compactH II regions.A LWS grating raster map of Sgr B2was also obtained dur-ing Revolution287as part of an open time program(see Cer-nicharo et al.1997for details).Fig.2displays the data aroundthe[O I]63µm line along two cuts oriented N-S and E-Wthrough Sgr B2.The[O I]63µm line intensity varies drasti-cally over the cut.The[O I]is seen in emission in most of thepositions,with a maximum180 south of Sgr B2.Around theposition of Sgr B2,the[O I]line gradually changes from anemission line into a line in absorption.3.DiscussionSgr B2,one of the most luminous star-forming regions in theGalaxy,consists of several compact H II regions(Gaume et al.1995)which are embedded in a massive molecular cloud.Thehydrogen column densities have been estimated to be a few1024cm−2in the2 core diameter(Scoville et al.1975).Sgr B2is optically thick even at far-infrared wavelengths where theJ.-P.Baluteau et al.:[O I]in absorption toward Sagittarius B2L35 opacity at100µm is estimated to be unity(Harvey et al.1977).In Sgr B2,the warm gas seen,e.g.,in the radio observations,is thus obscured completely by the associated molecular cloud.These high far-infrared opacities explain why the[O III]88µm(Dain et al.1978)and[O I]63µm(Lester et al.1981)lines werenot detected in the spectrum of SgrB2.The present ISO/LWSdata conﬁrm these early measurements(Fig.1)and the qualityof the data allows to detect the[O I]line in absorption.Although the spectral resolution of the grating is limited,useful conclusions can be derived from the present data con-cerning the abundance of atomic oxygen.Clearly,higher spec-tral resolution measurements such as obtained by Phillips et al.(1997)will permit a more detailed analysis including the studyof the velocity structure in the[O I]absorption line.The mean photoabsorption cross section of the[O I]63µmline isσ=5.093×10−18/(∆V kms−1)cm2where∆V is theline width in km s−1(e.g.,Allen1973-radiative lifetime fromBaluja&Zeippen1988).At a spectral resolution of0.29µm(∼1380km s−1),the measured3.0±0.5%absorption-linedepth of[O I]corresponds to a line equivalent width∆V ew=(41.4±7)km s−1.Assuming uniform absorption over a velocityrange∆V will result in a line optical depthτ=−ln(1−∆V ew/∆V)and a column density N O=1.963×1017×τ×∆V cm−2.In order to estimate the atomic oxygen abundance impliedby the[O I]63µm absorption,we consider two simple cases.First,we assume that the[O I]absorption is dominated by a lowdensity medium distributed uniformly in velocity along the lineof sight toward SgrB2.Adopting a typical density of1cm−3,the hydrogen column density is2.5×1022cm−2for a distance of8.5kpc to Sgr B2.Since there is no gas in the direction of Sgr B2at velocities smaller than−110or larger than+80km s−1(Scoville et al.1975),we will assume that∆V is less than∆V max=200km s−1.With∆V=∆V max,weﬁndτ=0.23and N O=9.1×1018cm−2,yielding N O/N H=3.6×10−4.In this simple approximation,the derived atomic oxygen abun-dance is half cosmic,suggesting that(1)atomic oxygen is thedominant form of gaseous oxygen and(2)the mean depletionof oxygen onto dust grains is,as expected,moderate.Sinceτis signiﬁcantly less than unity,these conclusions do not dependcritically on the exact value of∆V;using∆V=100insteadof200km s−1would increase N O by15%only.Similarly,theydo not depend much on the presence of clumping along the lineof sight provided that the[O I]optical depth does not exceedunity at any velocity.In the second case,we suppose that the[O I]absorptionis restricted to the most prominent molecular clouds.The ve-locity structure toward Sgr B2,as revealed by molecular lineabsorption,is complex(e.g.,Stacey et al.1987).Four main lay-ers contribute to the absorption,namely:(1)A very massivemolecular cloud associated with the Sgr B2complex itself at+63km s−1with N H2∼5×1023cm−2,(2)the expandingmolecular ring at–105km s−1with N H2∼4×1021cm−2,(3)the3-kpc arm(–43km s−1and N H2∼3×1021cm−2),and(4)the local gas at∼0km s−1with N H2roughly as in the two lattercomponents.The velocity widths of these components,deter-Fig.2.The spectra around[O I]63µm toward several directions alongN-S and E-W cuts in Sgr B2.The separation between successive posi-tions is90 .The central position(0,0)corresponds to SgrB2(Main)-α1950=17h44m10.6s,δ1950=−28o22 29 .Offset positions are givenin arcsec in the upper left corner of each panel.The source Sgr B2(North)is located at offset(0,90)in the North-South cutmined from radio absorption line studies,depend on the angularresolution of the observations.With a2 beam,the line widthsare8,11,15and20km s−1for the absorbing layers at–105,–43,+2and+63km s−1,respectively(Scoville et al.1975).Ata∼15”resolution,the widths are3,8,and12km s−1for thelast three components(Mehringer et al.1995).The ISO/LWSbeam being close to1.5 ,we adopt∆V SgrB2=20km s−1forthe Sgr B2cloud and∆V fore=30km s−1for the sum of thethree main foreground clouds.Altogether,the column densityof the three latter clouds is N H2∼1.1×1022cm−2.Assuming uniform absorption over the full velocity range ∆V molec=∆V SgrB2+∆V fore leads toτ=1.76and N O=1.7×1019cm−2.Considering30/50of this N O,the atomicoxygen abundance in the foreground clouds is N O/N H=4.6×10−4.We note,however,that∆V molec is not very sig-niﬁcantly larger than∆V ew.With the quoted uncertainties,N O/N H is thus estimated to vary from3.1to9.2×10−4,tobe compared to the cosmic abundance of oxygen[O]/[H]=8.5×10−4(Anders&Grevesse1989).In the relatively unlikelycase of a complete absorption over∆V SgrB2,N O/N H woulddecrease by30%.Conversely no solution exists if the absorp-LEL36J.-P.Baluteau et al.:[O I]in absorption toward Sagittarius B2tion is restricted to the range∆V fore:absorption by the Sgr B2cloud(over∆V SgrB2)should be at least50%,unless othersources of absorption are considered.Finally,τmay be muchlarger than the average value over restricted velocity ranges,also increasing N O/N H.The column density of atomic oxygen obtained in the foreground molecular clouds is thus consistentwith40to100%of oxygen being in atomic form.We note that the gigantic column density of the molecularcloud associated with Sgr B2is not directly relevant in the ab-sorption budget since only the envelope of the cloud(its”pho-tosphere”)is seen at far-infrared wavelengths due to the ob-scuration.Both the absorption and emission in the continuumshould be taken into account.Depending on whether a tempera-ture gradient is present and whether the population of the upperlevel of[O I]63µm differs from the Boltzmann population,theline may or may not appear in absorption.It is quite probablethat line scattering in the outskirts of the cloud willﬁnally leadto absorption,although this absorption may not be particularlydeep given that the scattering layer is nearly spatially coincidentwith the source of radiation and the LWS beam encompasses alarge fraction of the whole cloud.4.ConclusionThis Letter reports the detection in the ISO/LWS grating spec-trum of the[O I]63µm line in absorption toward Sgr B2.Atthe grating resolution of300,the depth of the line is∼3%ofthe continuum.This measurement implies a minimum columndensity of atomic oxygen along the line of sight toward SgrB2of1019cm−2.Although the Sgr B2molecular cloud must con-tribute to the absorption,no conclusions can be drawn concern-ing its atomic oxygen content.The abundance of atomic oxygen is thus at least40%of thecosmic abundance,implying that atomic oxygen is the dominantform of oxygen in the interstellar medium in the direction ofSgr B2.This conclusion agrees with the results of Poglitsch etal.(1996)who studied the line of sight toward DR21.In orderto analyse in more detail the contributions to the[O I]63µmabsorption of the molecular clouds distributed along the line ofsight toward SgrB2,higher spectral resolution observations arerequired.ReferencesAnders E.,&Grevesse J.-P.1989,Geochim.Cosmochim.Acta53,197Allen C.W.1973,Astrophysical Quantities,3rd edition,The AthlonePress(London)Baluja K.L.,&Zeippen C.J.1988,J.Phys.B.21,1455Bergin E.A.,Langer W.D.,&Goldsmith P.F.1995,ApJ441,222Black J.H.,&Smith P.L.1984,ApJ277,562Cernicharo J.et al.1997,A&A in pressClegg P.E.et al.1996,A&A315,L38Combes F.,&Wiklind T.1995,A&A303,L61Dain F.W.,Gull G.E.,Melnick G.,Harwit M.,&Ward D.B.1978,ApJ221,L17de Graauw et al.1996,A&A,315,L345Ehrenfreund,P.,Breukers,R.,d’Hendecourt,L.,&Greenberg,J.M.1992,A&A,260,431Gaume R.A.,Claussen M.J.,De Pree C.G.,Goss W.M.,&MehringerD.M.1995,ApJ449,663Harvey P.M.,Campbell M.F.,&Hoffman W.F.1977,ApJ211,786 Lacy,J.H.,Knacke,R.,Geballe,T.R.,&Tokunaga,A.T.1994,ApJ, 428,L69Lester D.F.,Werner M.W.,Storey J.W.V.,Watson D.M.,&TownesC.H.1981,ApJ248,L109Mehringer D.M.,Palmer P.,&Goss W.M.1995,ApJS97,497 Phillips,T.G.,Keene,J.B.,Lis,D.C.,Schilke,P.,Werner,M.W.,& Zmuidzinas,J.1997,in preparationPoglitsch A.,Herrmann F.,Genzel R.,Madden S.C.,Nikola T.,Tim-mermann R.,Geis N.,&Stacey G.J.1996,ApJ462,L43 Schulz A.,G¨u sten R.,Serabyn E.,&Walmsley C.M.1991,A&A246, L55Scoville N.Z.,Solomon P.M.,Penzias A.A.,1975,ApJ201,352Soﬁa U.J.,Cardelli J.A.,&Savage B.D.1994,ApJ430,650 Stacey G.J.,Lugten J.B.,&Genzel R.1987,ApJ313,859 Swinyard B.M.et al.1996,A&A315,L43van Dishoeck E.F.,Blake G.A.,Draine B.T.,&Lunine J.I.1993,in Protostars and Planets III,ed.E.H.Levy&J.I.Lunine(Tucson, Univ.Arizona Press)p.163van Dishoeck,E.F.,&Helmich,F.P.1996,A&A,315,L177 Viscuso P.J.,Stacey G.J.,Fuller C.E.,Kurtz N.T.,&Harwit M.1985, ApJ296,142This article was processed by the author using Springer-Verlag L a T E X A&A styleﬁle L-AA version3.。

雅思阅读分类最全词汇

第1 类自然与科技1. 1 如何减少闪电危害Reduce the Harm of Lightningantenna n. 天线breathing n. 呼吸cardiac arrest 向博[动]停止conductive adj. 传导的conductivity n. 传导性conductor of electricity 电导体conductor n. 导体confusion n. ，混乱，混淆connector n. 连接器crush vt. 压碎，碾碎，（使）变形cumulus n. 积云，堆积current n. 电流dangerous adj. 危险的disassociate v. （使）分离discontinue v. 停止，废止dwelling n. 住处electric power 电力，电功率electrical appliance 电器electrical potential 电能electrocution n. 电死evaporation n. 蒸发（作用）extinguisher n. 熄灭者，灭火器eyesignt n. 视力，目力fickle adj. 变幻无常的first aid （对伤患者的）急救forecast vt. 预测，预报，预兆；n. 预报fracture n. 破裂，骨折；v.（使）破碎，（使）破裂fuse box 保险丝盒，熔断器盒guide n. 领路人，引导者；vt. 操纵humid adj. 潮湿，湿润的，多湿气的indirect adj. 间接的，迂回的injure vt. 损害，伤害；vt. 伤害injury n. 伤害，侮辱insulating adj. 绝缘的isolated adj. 隔离的，孤立的lightning n. 闪电lightning protection 防雷法lightning storm 雷雨lightning target 闪电的目标Lightening proof adj. 防闪电的livestock n. 家畜，牲畜loss of hearing 听力丧失memory loss 记忆丧失moist adj. 潮湿的；n. 潮湿moisture-laden air 潮湿的空气mouth-to-mouth adj. 嘴对嘴的outdoors n. 户外；adv. 在户外，在野外pole n. 棒，柱，磁极，电极prompt medical attention 及时的医药治疗pulse n. 脉搏，脉冲resistance n. 阻力，电阻，阻抗resuscitation n. 复生，复兴rod n. 杆，棒shelter n. 掩蔽处，掩蔽，保护；v. 掩蔽，躲避shock n. 打击，震动，休克；vt. 使休克，使受电击Side flash n. 侧向闪光spread out 展开stoppage n. 中断stoppage of breathing 呼吸中断strike n. 打击take protective action 采取保护性措施take refuge 避难the positive and negative charges 正负电荷thunderstorm n. 雷雨，雷暴雨tingle vi. 造成麻刺的感觉；vt. 使感到刺痛unconscious adj. 不省人事的，未发觉的，无意识的unexpected adj. 想不到，意外的，未预料到的unplug v. 拔去（塞子、插头等）victim n. 受害人，牺牲品voltage n. [电工]电压，伏特数without proper protection 缺乏恰当的保护1.2 探索太空生命Life in the Outer Space abode n. 住所，住处absence n. 缺席，缺乏acceptor n. 接受者access v. 接近advanced civilization 先进的文明aerobic adj. 依靠氧气的，与需氧菌有关的agent n. 作用剂algae n. 藻类，海藻alteration n. 变更，改造alternative adj. 选择性的anaerobic adj. [ 微]没有空气而能生活的，厌氧性的analogous adj. 类似的，相似的analysis n. 分析antarctic adj. 南极的，南极地带的anticipated adj. 预先考虑到的antiquity n. 古代aquifer n. 蓄水层array n. 大批astronomer n. 天文学家atmosphere n. 大气，大气层，空气atmospheric water vapor 大气水蒸气attenuate v. 削弱avalanche n.&v. 雪崩bacteria n. 细菌biological adj. 生物学的bleak adj. 寒冷的，荒凉的carbon dioxide [化]二氧化碳catalyze vt. 催化cellular adj. 细菌的chamber n. 室chromatograph n. 套色复制clay n. 粘土,泥土clement adj. 宽厚的comment n.&v. 评论compact adj. 紧密的compelling adj. 引人注目的composition n. 成分compound n. 化合物concentrated adj. 集中的concentration n. 浓度conclusively adv. 最后的conduct n.&v. 进行confined adj. 被限制的confinement n. ( 被)限制,(被)禁闭conservatively adv. 适当的consistent adj. 一致的constituent n. 要素constraint n. 约束ncontradict vt. 同……矛盾controversy n. 论争crack n. 裂缝crater n. 坑cretaceous adj. [ 地]白垩纪的dam n. 水坝，障碍data n. 资料，数据debris n. 碎片，残骸decompose v. 分解demonstrate v. 证明deplete vt. 耗尽depletion n. 损耗deposit n. 堆积物desiccated adj. 干的，粉状的diffuse v. 扩散disassociate v. （使）分离disaster n. 灾难，灾祸discount n. 打折扣dissolve v. 溶解distributed adj. 分布的distribution n. 分布状态dweller n. 居住者，居民ecosystem n. 生态系统embedded adj. 内含的emission n. 散发，喷射enhance n. 提高envision n.想象equatorial region 中纬区，赤道区equator n. 赤道eruption n. 爆发essentially adv. 本质上evaporate v. （使）蒸发evolution n. 演变，进化existence of life 生命的存在exposed adj. 暴露的extract vt.& n. 析取fascination n. 吸引力Fe-rich clay 含丰富铁质的黏土flash adj. 突发的flow n. &v. 流动flux n. [ 物]流量，通量formation n. 形成，构成fossil adj. 化石的freeze v.（使）结冰，冻结fuel vt. 激化functional adj. 功能的gas chromatograph 气相色谱仪generating n.发生，产生geological adj. 地质学的，地质的geothermal adj. 地热的geyser n.间歇泉guarantee n.保证gully n.冲沟，溪谷habitable adj. 可居住的harsh adj. 荒芜的，苛刻的headquarters n.总部hemisphere n.半球high spatial resolution 高空间分辨率high resolution photograph 高辨析率／清晰度的相片hostility n.敌对，对抗humidity n.湿气，湿度hydration n.水合，水合作用hydrogen n.氢hydrothermal adj. 热水的hypothesize v.假设imaging n.成像inconsistent adj. 不一致的，矛盾的incorporated adj. 组成公司的，合成一体的incubation period （接种后的微生物）保温培养期incubation n.培养期indicate vt. 显示indicative adj. 指示的，预示的indigenous adj. 本土的infrared imaging system 红外线成像系统infrared adj. 红外线的inhospitable adj.（地带、气候等）不适合居住的inorganic adj. 无机的interaction n.交互作用internal adj. 内在的interpretation n.解释intriguing adj. 引起兴趣（或好奇心）的investigation n.调查，研究investigator n.调查人involve vt. 包括ionize vt. 使离子化isolated adj. 孤立的jurisprudence n. 法学lander n.登陆者latitude n.纬度launch n.& v. 发射（导弹、火箭等）layperson n.外行lichen n.[ 植]青苔，地衣local n.场所LR=laboratory reactor n.实验室反应堆lubricated adj. 润滑了的manned space flight 载人航天飞行mariner n.水手Martian adj. 火星的mass of data 大量数据mass spectrometer 质谱测量仪mechanism n.机制merit n.价值meteorite n.陨星microbe n.微生物microbial adj. 微生物的microbiological life 微生物的microorganism n.[ 微生]微生物migrate vt. 使移居，使移植mimic vt. 摹拟mineral n.矿物，矿石molecular adj. 分子的molecule n.[ 化]分子mount v.增长multi-cellular organism 多细胞生物休National Aeronautis and Space Administration (NASA) （美国）国家航空和宇宙航行局notion n.意见nutrient n.营养物observational date 观测资料[数据]orbiter n.人造卫星organic adj. 有机的organism n.生物体，有机体oxidant n.氧化剂oxidize agent 氧化剂oxygen n.氧paradise n.天堂particulate n.微粒patch n.碎片percolating n.渗透peroxide n.[ 化]过氧化物，过氧化氢pervasive adj. 普遍深入的planetary adj. 行星的plateau n.（上升后的）稳定水平（或时期、状态）plug n.塞子pockmarked adj. 有麻点的polar adj. 两极的pole n.极porous adj. 多孔渗水的portable adj. 轻便的pose v.形成postulate n.& v. 假定precipitate n.沉淀物predominance n.优势preponderance n.优势primitive microbe 简单微生物principal adj. 主要的，首要的prior to 在前，居先prior adj. 在前的problematic adj. 有疑问的prospect n.前景radioactive carbon 放射性碳radioactive adj. 放射性的，有辐射能的ravine n.沟壑，峡谷reactant n.反应物reconcile with 与……和解regolith n.[ 地质]风化层，土被reinforce n.加强release n.& vt. 释放remote sensing instrument 遥感仪器remote sensing 遥感，遥测，远距离读出reproduce v.再生reside in 居住residual adj. 剩余的，残留的respiration n.呼吸作用respire v.呼吸retrieve v.找回revive v.（使）复活，回想rift n.裂口，长狭谷rule out 排除sample n.标本，样品sediment n.沉淀物seepage n.渗流simulate vt. 模拟slope n.斜坡，斜面solar adj. 太阳的，日光的solfatara n.[ 地]硫质喷气孔solubility n.溶度sophisticated adj. 高级的，精密的space probes 宇宙探测器spacecraft n.太空船spatial resolution 空间分辨率spectrometer n.[ 物]他光计speculation n.思索startling adj. 令人吃惊的subsequently adv. 随后substantial adj. 大量的subsurface adj. 地下的suffice v.足够sufficient adj. 充分的，足够的sulfide n.< 美＞[化]硫化物sulfur n.[ 化]硫磺，硫黄superoxide n.过氧化物，超氧化物surveyor n.检查员survey n.& vt. 调查tag vt. 加标签于terminal n.终端terrestrial adj. 陆地的theological adj. 神学上的theorise v.理论化ultimately adv. 最后ultraviolet radiation 紫外线ultraviolet adj. 紫外线的underground water 地下水unresolved adj. 未解决的uptake n.举起vent n.出口volume n.量，体积wavelength n.[ 物](无线电)波长xenon n.氙(惰性气体的一种，元素符号) xenon-lamp 氙灯1.3 热带雨林Tropical Rainforest abounding adj. 丰富的，大量的accelerate v.加速，促进acre n. 英亩alkaloid n.生物碱angler n.钓鱼者appreciate vt. 赏识，欣赏approximate v.近似，接近aquatic ecosystem 水生态系统avocado n.鳄梨awe-inspiring adj. 令人敬畏的bald eagle [动]秃头鹰basic food supplies 主食的供给be compatible with 与……兼容的，协调的be conquested by a totalitarian government 被极权主义政府征服be perceived as 被视为biochemist n.生物化学家biodiversity n.生物多样性biological and economic treasure 生物和经济的财富biological corridor 生物走廊biological diversity 生物多类状态，生物差异biological heritage 生物遗产biological integrity 生物的完整性biological treasure 生物宝藏biologically diverse 生物多样的bison n.美洲或欧洲的野牛black pepper 黑胡椒blame n.& vt. 谴责，责备bountiful gift 慷慨的礼物bountiful adj. 慷慨的，宽大的branded adj. 打有烙印的buffer zone 缓冲区域bull troutn 鲑鱼的一种bulldozer n.推土机bureaucracy n.官僚，官僚作风，官僚机构by virtue of 依靠，由于cancer-fighting drug 抗癌药物carnivore n.食肉动物，食虫植物cashew n.腰果catastrophe n.大灾难，大祸cayenne n.辣椒chainsaw n.链锯chocolate n.巧克力cinnamon n.肉桂citizenry n.公民，市民clear cutting 清除林木，开垦土地clove n.丁香coconut n.椰子concern n.( 利害)关系,关注congressional mandate 国会委托conifer n.[ 植]松类，针叶树connected habitat 连接成一片的动物栖息地conservation biology 保护生物学consideration n.考虑，需要考虑的事项constituent n.要素core area 核心区域culprit n.罪魁祸首cure n.治疗，疗法decimation n.大批杀害deforestation n.采伐森林deplete vt. 耗尽descendant n.后代designated adj. 指定的，派定的die out 灭绝，逐渐消失dinosaur n.恐龙disperse v.( 使)分散，(使)散开，疏散doomed adj. 命中注定的ecological integrity 生态完整economic collapse 经济崩溃ecosystem n.生态系统elk n.[ 动]麋鹿encompass v.包围，环绕endangered plant and animal 濒危的动植物endangered adj.（生命等）有危险的，有灭绝危险的，将要绝种的energy depletion 能源耗尽entomologist n.昆虫学家entrenched adj. 确立的,(风俗习惯)不容易改的environmental damage 环境损害environmental villain 破坏环境的恶棍eons n.永世，无数的年代equate v.等同于escalate v.逐步增强eviction n.驱逐exploiter n.开拓者，开发者extinction of plants and animals 动植物的灭绝extinction n.消失，消灭extinguish vt. 消灭，熄灭falcon n.[ 动](猎鸟用的)猎鹰fall victim to 成为……的牺牲品far-sighted founder 具有远见的奠基人fig n.无花果firewood n.木柴，柴火fishery n.渔业，水产业flock n.( 禽、畜等的)群forest ecosystem 森林生态系统forgive vt. 宽恕，原谅fossil n.化石fragmentation n.分裂，破碎fragmented adj. 断开的，支离破碎的fresh water 淡水fuel n.燃料fungus n.菌类，蘑菇galaxy n.银河generosity n.慷慨，宽大ginger n.生姜global warming 全球变暖grazing land for cattle 牧场grizzly bear 大灰熊grizzly n.灰熊guava n.番石榴habitat n.( 动植物的)生活环境，栖息地，居留地harbor vt. 为……提供住所；保护hectare n.公顷herds of 成群heritage n.遗产，继承权，传统immense adj. 巨大的imperil vt. 使处于危险，危害in trust 被托管indescribable adj. 难以形容的indigenous Indian tribe 当地的印第安部落industrial raw material 工业原材料inner dynamics 内在动力intact habitat 未被破坏的动植物生活环境intact adj. 完整无缺的interdependent adj. 相互依赖的interlocking network 联锁网络intertwine n.（使）纠缠，（使）缠绕intervention n.干涉intricate and fragile system 复杂脆弱的系统invertebrate adj. 无脊椎的；n.无脊椎动物irreplaceable adj. 不可替代的irresponsible stewardship 不负责任的管理者legacy n.遗赠(物)，(祖先传下来的)遗产lemon n.柠檬lifeblood n.生命必须的血液，活力的源泉lobby v.游说议员，对（议员）进行疏通loss of biodiversity 生物多元化的消失loss of genetic and species diversity 基因和物种多样性的消失lucrative market 有利可图的市场lynx n.[ 动]山猫，猞猁magnitude n.巨大，(影响的)重大majesty n.雄伟malaria epidemic 疟疾流行mango n.芒果massive deforestation 大面积的砍伐林木medicinal value 药用价值metabolite n.代谢物microorganism n.微生物multi-national logging company 跨国伐木公司myriad n.无数人或物；adj. 无数的natural habitat 自然栖息地，(动植物的)生活环境natural tropical forest 天然的热带雨林nut n.坚果on a perpetual basis 永久地outcry n.大声疾呼oxygen n.[ 化]氧pacific salmon 大鳞大麻哈鱼属paradise n.天堂peregrine n.隼adj. 外来的，移位的pharmaceutical manufacturer 制药厂商pineapple n.菠萝poacher n.偷猎者pond n.池塘prescription drug 处方药private timber company 私营木材公司profound and devastating 深远和破坏性的public asset 公共财产put an end to 结束，终止quantify v.量化rain forest (热带的)雨林rainforest deforestation 砍伐雨林rainforest ingredient 雨林成分rainforest reserve 雨林保护区rainforest n.雨林ranch n.大牧场recreational from 娱乐形式release n.& vt. 释放renewable and sustainable resource 可恢复的可持续的资源replenish v.补充reproduce v.繁殖，再生resource-dependent industry 依赖于资源的行业restore vt. 恢复，使回复，修复riparian area 河岸salmon n.[ 鱼]鲑鱼，大麻哈鱼sedimentation n.沉淀，沉降self-serving adj. 自私的shamans n.僧人，巫师shelter n.庇护所shoreline n.海岸线short-sighted adj. 短视的short-term utilization 短期利用siltation n.沉积作用，淤积slaughter jaguar, ocelot, caiman and otter 屠杀美洲虎、虎猫、凯门鳄和水獭soil erosion 土壤侵蚀spice n.香料squash n.南瓜staggering adj. 令人惊讶的stake n.木桩，危险store n.& vt. 储藏，存储streamside n.河滨，河边地带stump n.树桩subarctic adj. 亚北极区的subsidize n.资助，津贴sugar cane 蔗糖sustain vt. 维持，支持sustainable adj. 可持续的terrestrial evolution 陆地进化terrestrial n.陆地the brink of ecological meltdown 生态崩溃的边缘the British Isles 大不列颠群岛the rate of destruction 破坏的速率the survival and well-being of man 人类的生存和幸福thrive v.兴旺，繁荣，茁壮成长，旺盛timber production 木材生产timber n.木材timelessness n.永恒tragic consequence 悲剧性的结局tropical rainforest 热带雨林tropical tree 热带树林tropical adj. 热带的，热情的tundra n.苔原，冻土地带unbroken adj. 未破损的，完整的unsustainable adj. 不能证实的，不能成立的，不能支持的vanilla n.香草vincristine n.[ 药]长春新碱（一种抗肿瘤药）virgin forest 原始的、未采伐过的森林wasteland n.荒地，未开垦地watershed n.分水岭western pharmaceutical 西药wilderness recreation recreation 野外娱乐wilderness n.荒野，荒地wildlife n.野生动植物yam n.山药zealot n.狂热者1.3 火山爆发The Eruption of Volcano abundant adj. 丰富的，富余的accretion n.增长accumulation n.积聚，堆积物active volcano 活火山Alaska Volcano Observatory 阿拉斯加州火山观察站aleutian island 阿留申群岛（环布于阿拉斯加半岛尖端的弧形岛屿）alternating layers of lava flows 熔岩流的交互叠层aluminum n.[ 化]铝Archean adj.[ 地质]太古代的archeology n.考古学ascending adj. 上升的，向上的ash particle 灰烬微粒awesome adj. 引起敬畏的，可怕的basaltic lave 玄武岩火山石basin-shaped adj. 盆状的beat out 敲平belated adj. 误期的，迟来的blacksmith n.铁匠blanket n.毯子，覆盖blast n.一股(气流)，爆炸，冲击波blob n.一滴，水滴blocky adj. 短而结实的，斑驳的bomb n.火山口喷出的大堆球状熔岩bowl-shaped crater 碗形的火山口bubble n.泡沫bulbous adj. 球根的buoyancy n.浮性，浮力calcium n.[ 化]钙（元素符号Ca）caldera n.[ 地质]喷火山口，凹陷处。

物理学2007-2009年4区SCI分区及影响因子

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化学专业英语常用词5

Analytical chemistry 分析化学Qualitative ['kwɔlitətiv] adj 定性的Quantitative ['kwɔnti,tətiv; -,teitiv] adj 定量的Qualitative analysis 定性分析Quantitative analysis 定量分析Separation [sepə'reiʃ(ə)n] n 分离Classical method 经典方法/ wet chemistry method 湿化学法Precipitation [pri,sipi'teiʃ(ə)n] n 沉淀Extraction [ik'strækʃ(ə)n; ek-] n 萃取Distillation [,disti'leiʃn] n 蒸馏Color ['kʌlə(r)] n 颜色Odor 气味Melting point 熔点Weight [weit] n 质量V olume ['vɔljuːm] n 体积Instrumental method 仪器法Light absorption 光吸收Fluorescence [fluə'res(ə)ns; flɔː-] n 荧光Conductivity [kɔndʌk'tiviti] n 导电性Chromatography [,krəumə'tɔgrəfi] n 色谱分析Electrophoresis [i,lektrə(u)fə'riːsis] n 电泳Sampling ['sɑːmpliŋ] n 取样Reagent Grade 试剂级别Primary Standard Grade 初级标准级Analytical Reagent Grade 分析纯Guaranteed Reagent Grade 保证试剂级Organic Reagent Grade 有机试剂级Chemically Pure Grade 化学纯Technical Grade 工业级Analytical balance 分析天平Desiccator ['desikeitə] n 干燥器Desiccant ['desik(ə)nt] n 干燥剂Hygroscopic [haigrə(u)'skɔpik] adj 吸湿的Crucible ['kruːsib(ə)l] n 坩埚Beaker ['biːkə] n 烧杯Dropping pipet 滴定管Graduated cylinder 量筒Pipet [pi'pɛt] / pipette [pi'pet] n 移液管Buret [bju'rɛt] / burette [bju'ret] n 滴管V olumetric flask 容量瓶Automatic [ɔːtə'mætik] adj 自动的Tap P199Stopcock ['stɔpkɔk] n 活塞Error ['erə] n 误差Uncertainty [ʌn'sɜːt(ə)nti; -tinti] n 不确定Mean [miːn] n 平均值Arithmetic mean 算数平均值Media ['miːdiə] n 中间数Accuracy ['ækjurəsi] n 精确度Precision [pri'siʒ(ə)n] n 准确度Absolute error 绝对误差Percent relative error 相对误差百分数Spread [spred] n 扩展度、分布Range [rein(d)ʒ] n值域、范围Standard deviation 标准偏差Variance ['veəriəns] n 方差Coefficient of variation 方差系数Deviation from the mean 与平均值间的差P201Deviation [diːvi'eiʃ(ə)n] n 偏差Absolute standard deviation 绝对标准偏差Relative standard deviation 相对标准偏差Percent relative standard deviation 相对标准偏差百分数Systematic [sistə'mætik] adj 系统的/ determinate [di'tɜːminət] adj 确定的Sampling error 取样误差Method error 方法误差Measurement error 操作误差Personal error 个人误差Random ['rændəm] adj 随机的/ indeterminate [,indi'tɜːminət] adj 不确定的True value 真实值Bia 偏差P201Sample ['sɑːmp(ə)l] n 样品Population [pɔpju'leiʃ(ə)n] n 总体Probability distribution 分布几率Gaussian ['ɡausiən] adj 高斯的Normal didtribution 正态分布Population’ s centralTrue mean valuePopulation standard deviation 总体标准偏差Confidence interval 置信区间Confidence level 置信水平Confidence limit 置信限度t-test t检验F-test F检验Q-test Q检验Detection limit 检出限Gravimetric analysis 质量分析Precipitation method 沉淀法V olatilization method 挥发法Titrimetric method 滴定法V olumetric analysis 体积分析Primary standard 初级标准Secondary standard 二级标准Standard solution 标准溶液Direct method 直接方法Standardization 标定Secondary standard solution 二级标准溶液Titration [tai'treiʃən] n 滴定Equivalence point 等当点,等效点,当量点Back titration 反滴定End point 终点Titration error 滴定偏差Indicator ['indikeitə] n 指示剂Titration curve 滴定曲线Litmus ['litməs] n 石蕊Phenolphthalein [,fiːnɔl'(f)θæliːn; -'(f)θe il-] n 酚酞Bromothymol blue 溴百里酚蓝Acid-base titration 酸碱滴定Complexometric titration 络合滴定Redox titration 氧化还原滴定Precipitation titration 沉淀滴定Potentiometric [pəu,tenʃiə'metrik] adj 电势测定的V oltammetry [vəul'tæmitri] n 伏安法Coulometry [ku'lɑmitri] n 库伦发Conductometry [kən'dʌktəmetri] n 电导测定法Dielectrometry 介电滴定Potentiometric method 电势测定方法Potentiometry 电势测定法Potentiometer 电位计Reference electrode 参考电极Indicator electrode 指示电极Junction potential 接界电势Coulometric method 库伦法Controlled-potential coulometry 控制电位电势法Potential coulometry 恒电位库伦法Controlled-current coulometry 控制电流库伦法Amperostatic coulometry 恒电流库伦法Electroanalysis [i,lektrəuə'næləsis] n 电分析Coulometric titration 库伦滴定Potentiostat [pəu'tenʃiəstæt] n 稳压器Coulometer [ku'lɑmitɚ] n 库伦计Galvanostat / amperostat 恒流器Coulomb ['kuːlɔm] n 库伦V oltammetry [vəul'tæmitri] n 伏安法V oltammogram 伏安图Working electrode 工作电极Reference electrode 参考电极Auxiliary electrode 辅助电极Saturated calomel electrode 饱和甘汞电极Linear-scan voltammetry 线性扫描伏安法Hydrodynamic voltammetry 流体动力学伏安法Polarography [,pəulə'rɔgrəfi] n 极谱法Amperometry 电流滴定法Stripping voltammetry 溶出伏安法Anodic [æn'ɑdik] adj 阳极的Cathodic [kə'θɔdik] adj 阴极的Adsorptive [æd'sɔrptiv] adj 吸附的Cyclic voltammetry 循环伏安法Alternating current 交替电流Chrono-conductometrySpectroscopy [spek'trɔskəpi] n 光谱学Emission [i'miʃ(ə)n] n 发射Scattering ['skætəriŋ] n 散射Spectrometer [spek'trɔmitə] n 分光仪Prism ['priz(ə)m] n 棱镜Diffraction grating 衍射光栅Monochromatic [mɔnə(u)krə'mætik] adj 单色的Half-mirrored 半透明反射的Sample beam 样品光束Reference 参比Electronic excitation 电子激发Transition [træn'ziʃ(ə)n; trɑːn-; -'siʃ-] n 跃迁Molar absorptivity / molar extinction coefficient 摩尔吸光/消光系数Hypsochromic / blue shift 蓝移Bathochromic / red shift 红移Beer-Lam-bert law朗伯比耳定律Absorbance [əb'zɔːb(ə)ns; -'sɔːb(ə)ns] n 吸光度Transmittance [trænz'mit(ə)ns; trɑːnz-; -ns-] n 透射比Infrared spectrophotometer 红外分光光度计Far-infrared 远红外Rotational 振动的Mid-infrared 中红外Rotational-vibrational 旋转振动的Overtone / harmonic vibration 谐振Resonant frequency 共振频率Vibrational mode 振动模式Vibrational degree of freedom 振动自由度Stretching ['stretʃiŋ] n伸缩、拉伸、伸长Bending ['bendiŋ] n 弯曲Scissoring ['sizəriŋ] n剪刀式摆动、剪,剪切Rocking ['rɔkiŋ] n左右摇摆，摇摆, 摇动Wagging [wæg] n上下摇摆，推移,摇摆Twisting ['twistiŋ] n扭摆，扭曲Symmetric [si'metrik] adj 对称的Antisymmetric stretching 反对称伸缩Fourier transform 傅立叶转换Functional group region 官能团区Fingerprint region 指纹区Fourier transform infrared (FTIR)spectroscopy 傅立叶转换红外光谱Inter ferometer 干涉仪Inter ferogram 干涉图Atomic absorption spectroscopy (AAS) 原子吸收光谱Atomization [,ætomi'zeʃən] n 原子化Flame atomization 火焰原子化Furnace ( electrothermal) atomization 炉子原子化Atomic emission 原子发射Inductively coupled plasma (ICP) 感应耦合等离子体Emission line 发射线Flame photometry火焰光谱Atomic fluorescence 原子荧光Nuclear magnetic resonance (NMR) 核磁共振Nuclear magnetic resonance spectroscope 核磁共振光谱Intrinsic magnetic moment固有磁矩Angular moment角动量Nonzero spin 非零自旋P219Resonant frequency 共振频率Nuclear shielding 核屏蔽Chemical shift 化学位移Tetramethylsilane 四甲基硅J-coupling J耦合Scalar coupling标量耦合Spin-spin coupling 自旋耦合Splitting ['splitiŋ] n 分裂Pascal’ s triangle帕斯卡三角Doublet ['dʌblit] n 双重峰Triplet ['triplit] n 三重峰Quartet [kwɔː'tet] n 四重峰One-dimensional technique 一维技术Two-dimensional technique 二维技术Time domain NMR spectroscopic technique 时域核磁共振光谱技术Solid state NMR spectroscopy 固态核磁共振光谱法Mass spectrometry (MS) 质谱学Mass-to-charge ratio 质荷比Molecular ion 分子离子Fragment ion 碎片离子Mass spectrum 质谱Base peak 基峰Mass spectrometer 质谱仪Ion source 离子源Mass analyzer 质量分析器Ion detector 离子检测器Electron impact ( EI ) ionization 电子轰击离子化Chemical ionization 化学电离Electrospray ionization ( ESI) 电喷射离子化Matrix-assisted laser desorption / ionization ( MALDI) 基质辅助激光解吸/电离Inductively coupled plasma (ICP)Sector field mass analyzer扇形磁场质谱分析仪Time-of-flight (TOF) analyzer 飞行时间分析仪Quadrupole mass analyzer 四级杆质量分析器Tandem mass spectrometry 串联质谱法Chromatography [,krəumə'tɔgrəfi] n 色谱分析法Mobile phase 流动相Differential partitioning 差动分隔Stationary phase 稳定相Partition coefficient 分配系数Retention [ri'tenʃ(ə)n] n 保留Elution [i'lju:ʃən] n 洗出液Elute [i'l(j)uːt] v 洗提Eluent['ɛljuənt] n 洗脱液Eluotropic series洗脱序(洗脱液洗脱能力大小的次序)Chromatogram 色谱图Distribution constant 分配常数Retention time 保留时间Retention volume 保留体积Dead time 死时间V oid time 空隙时间V oid volume 空隙体积Baseline width 基线宽度Band broadening 谱带增宽Resolution 分辨率Capacity factor 容量因数,容量因子Selectivity factor选择系数，选择因子Theoretical plate 理论塔板Peak capacity 最高容量Column chromatography 柱层析(法), 柱色谱(法)Planar chromatography平面色谱法Paper chromatography 纸色谱法Thin layer chromatography 薄层色谱Retention factor 保留因子Gas chromatography 气相色谱gas-liquid chromatography 气液色谱Capillary column 毛细管柱Packed column 填料柱,填充柱,填料塔Liquid chromatography (LC) 液相色谱法High performance liquid chromatography (HPLC) 高效液体色谱Normal phase 正相Reverse phase 反相Affinity chromatography (AC) 亲合色谱法Supercritical fluid chromatography 超临界流体色谱法Ion exchange chromatography 离子交换色谱法Ion exchange resin 离子交换树脂Fast protein liquid chromatography (FPLC) 快速蛋白质液相层析Size-exclusion chromatography (SEC) 体积排除色谱法Gel permeation chromatography (GPC) 凝胶渗透色谱法Hydrodynamic diameter 流体力学半径Hydrodynamic volume 流体力学体积Electrophoresis [i,lektrə(u)fə'riːsis] n 电泳Capillary zone electrophoresis 毛细管电泳Electroosmotic flow 电渗透流Micellar electrokinetic capillary chromatography 胶束电动毛细管色谱p226 Capillary gel electrophoresis 毛细管凝胶电泳Capillary electrochromatography 毛细管电色谱Optical microscopy 光学显微镜Electron microscopy 电子显微镜Scanning electron microscopy (SEM) 扫描电子显微术Transmission electron microscopy (TEM) 透射电子显微镜法Scanning probe microscopy (SPM) 扫描探针显微术Atomic force microscopy (AFM) 原子力显微镜Thermogravimetry (TG) 热重分析法Differential thermal analysis (DTA) 热分析Differential scanning calorimetry (DSC) 差热扫描量热计Dynamic mechanical analysis (DMA) 动态力学分析Raman spectroscopy (RS) 拉曼光谱Auger electron spectroscopy (AES) 俄歇电子能谱学Photoelectron spectroscopy (PES) 光电子能谱Electron spectroscopy for chemical analysis (ESCA) 化学分析用电子能谱学X-ray photoelectron spectroscopy (XPS) X射线光电子能谱学X-ray fluorescence (XRF) X射线荧光X-ray powder diffractometry (XRD) x射线粉末衍射Electrochemiluminescence (ECL) 电致化学发光。

2012-7-6-物理学概论之七-原子与分子物理.ppt [修复的]

（2）研究利用Stark能级移动控制极性NaK分子布居转移的论文 “Steering population transfer of a five-level polar NaK molecule by Stark shifts”发表在Chem. Phys., 344 (2008), 121。（3）研究利用激光诱导连续结构控制非极性Li2分子布居转移的论文 “Steering population transfer via continuum structure of the Li2 molecule with ultrashort laser pulses” 发表在Chem. Phys.，348 (2008), 39 。（4）研究利用飞秒脉冲链对分子进行振转量子调控的论文 “Rovibrational manipulation of molecular quantum state by a train of ultrashort pulses”发表在 Chem. Phys. Lett., 491 (2010), 156。
(1)分子定向(orientation)：容器中大量分子的特征矢量（如：角动量、电偶极矩、分子轴等）方向沿着（或者大体上沿着）空间某一方向分布。
Z
Z
J
J
（a）正方向
（b）负方向
图4.1. 分子角动量的定向
(2)分子取向(alignment) 容器中大量分子的特征矢量方向沿着（或者大体上沿着）空间某一方向及其相反方向等几率分布。
研究分子在飞秒强激光场中激发、解离、电离动力学是原子分子物理的主要研究方向之一。下面介绍几个热点研究课题： 1.研究小分子在飞秒和亚飞秒脉冲强激光场中超阈值解离和超阈值电离动力学。
(1) 研究极性分子NaK的超阈值电离

[核磁共振讲义]第一章—核磁共振基础知识

第一章核磁共振基础知识核磁共振（NMR）是指核磁矩不为零的核，在外磁场的作用下，核自旋能级发生塞曼分裂，共振吸收某一定频率的射频辐射的物理过程。

核磁共振是波谱学的一个分支，研究核磁共振现象与原子所处环境如分子结构，构象，分子运动的关系及其应用。

生物化学，分子生物学的发展对生物大分子空间结构的测定提出越来越高的要求，而逐渐形成一门新兴的交叉学科即结构生物学。

结构生物学已成为生命科学研究的前沿领域和热点。

核磁共振波谱学是结构生物学的一种重要的研究手段，核磁共振波谱学各种最新技术的出现和发展往往与结构生物学密切相关。

如3D，4DNMR。

简史：1924 Pauli从光谱的超精细结构推测某些原子核有核磁距，能级裂分，共振吸收1936 Gorter试图观察LiF中7Li的吸收，未能成功，因样品弛豫时间太长1945－1946 F.Bloch(Stanford), H2O 感应法E.M.Purcell(Harvard), 石蜡吸收法1946－1948 奠定了理论基础1952年共得诺贝尔物理奖1951 Arnold et al 乙醇1H化学位移精细结构1957 Saunders et al 核糖核酸酶40 MHz的1H谱(1965 Cooley, Tukey FTT)1966 R.R. Ernst 脉冲NMR理论1971 Jeener 2DNMR原理1984 K. Wuethrich用NMR解蛋白质溶液结构1945-1951 奠定理论和实验基础1951-1965 CW－NMR发展，双共振技术1965-1970～PFT－NMR发展1970～--- 2D－NMR，MQT－NMR，SOLID－NMR，自旋成象技术核磁共振可以用于研究有机分子的化学结构，代谢途径，酶反应的立体化学信息，生物大分子的溶液构象，分子间相互作用的细节，化学反应速率，平衡常数，还可用来研究分子动力学，包括分子内的基团运动，以及生物膜的流动性。

细胞和活组织中化学成分的分布及交换过程，等等。

propane

Quasiclassical trajectory calculations of collisional energy transfer in propane systemsApichart Linhananta and Kieran F.Lim*¤Centre for Chiral and Molecular T echnologies,School of Biological and Chemical Sciences,Deakin University,Geelong,V ictoria3217,Australia.E-mail:lim=.auRecei v ed6th December1999,Accepted27th January2000Published on the Web9th March2000Quasiclassical trajectory calculations of collisional energy transfer(CET)and rotational energy transfer from highly vibrationally excited propane to rare bath gases are reported.The calculations employed atomÈatom pairwise-additive Lennard-Jones,Buckingham exponential and hard-sphere intermolecular potentials to examine the dependence of CET on the intermolecular potential and to establish a protocol for future work on larger alkane systems.The role of the torsional(internal)and molecular(external)rotors in the energy-transfer mechanism were parison of the results with our earlier work on ethane]neon systems(A. Linhananta and K.F.Lim,Phys.Chem.Chem.Phys.,1999,1,3467)suggests that the internal and external rotors play a signiÐcant role in the deactivation mechanism for highly vibrationally excited alkanes.I.IntroductionGas-phase chemical reaction rates are strongly dependent on intermolecular collisional energy transfer(CET).CET is a vital component in any combustion-model and atmospheric-model systems.The only experimental CET quantities for hydrocarbon fuel molecules have been inferred““indirectlyÏÏfrom measurements of pressure-dependent reaction rates.1h3 Despite this,there have been no systematic theoretical dynamics studies of CET of hydrocarbon and halogenated hydrocarbons.In fact,most theoretical studies have been on small molecules.3h14The exceptions are the quasiclassical tra-jectory(QCT)calculations of azulene,toluene,benzene and hexaÑuorobenzene systems.15h23We have recently reported QCT calculations for highly vibrationally excited ethane in neon bath gas.24This and the recent work by Svedung et al. are,to our knowledge,theÐrst theoretical CET studies of an alkane with internal rotors.24,25Comparisons of theoretical and experimental studies of CET show that many of the dominant energy transfer mecha-nisms in small molecules are also present in large mol-ecules.3h6However,there are several di†erences between large-substrate and small-substrate behaviours.A notable example is that in the CET from a““smallÏÏsubstrate to a rare gas collider the trend He[Ne[Ar is observed,26h28 whereas the opposite trend of He\Ne\Ar is observed for ““largeÏÏsubstrates.29h39Theoretical studies of CET on small molecules employing various techniquesÈquantum,semi-classical and classical dynamicsÈall have correctly predicted the small-substrate behaviour.40,41This is not the case for large-substrate systems where QCT simulations incorrectly found the same smallsubstrate trend.15h18The discrepancy may be due to the lack of reliable data on the intermolecular potential surface involving large molecules and is most likely to be manifested in systems with the small collider helium bath gas.42,43¤Lim Pak Kwan.The aforementioned QCT calculations of large-substrate molecules have been on aromatic hydrocarbons because they have been most amenable to experimental studies using spec-troscopic probes.There have been fewer studies28,44h47on alkanes and branched-alkanes,which are the main com-ponents of common combustion fuels,and their halogenated analogues,which are important in ozone and““greenhouseÏÏchemistry.TheÐrst most obvious di†erences between alkanes and aromatics are their shapes,which are expected to a†ect the rotational energy transfer(RET).Since rotation to trans-lation(R]T)energy transfer and vibration to rotation (V]R)energy transfer are often more efficient than vibration to translation(V]T)energy transfer,this can have a strong inÑuence on the overall CET.Another crucial aspect is theÑexibility of alkanes.QCT simulations of alkanes would require the development of an efficient algorithm for sampling conformer space.Related to theÑexibility,as well as to RET,is the role of internal rotors in the CET mechanism.QCT calculations of highly vibra-tionally excited ethane in neon bath gas show that there is an interrelationship between the internal methyl rotors and the external rotation giving rise to V]torsion,R energyÑow in theÐrst collision,resulting in an““enhancedÏÏCET in sub-sequent collisions.24The same e†ect is also observed in experiments on the deactivation of highly vibrationally excited benzene and toluene,where toluene has much larger CET values than benzene.37This e†ect suggests that the torsional rotors in alkanes are important.Since the use of intramolecular torsional potential terms (nine such terms for each additional methylene unit)24plus a sampling of the conformational space may prove to be cost-prohibitive for large(r)alkane systems,there is a need to establish an e†ective protocol for QCT alkane simulations. Use of a hard-sphere potential will reduce a substrateÈcollider collision into a sequence of““sudden-impactÏÏatomÈatom encounters.Furthermore,there is no need to calculate molec-ular interactions at medium-to-large atomic separations.This paper““benchmarksÏÏCET using a hard-sphere potential against the more-commonly used Lennard-Jones andDOI:10.1039/a909614k Phys.Chem.Chem.Phys.,2000,2,1385È13921385This journal is The Owner Societies2000(Buckingham-type exponential-6models,by performing QCT calculations on the propane ]monatomic collider systems.The role of the torsional (internal)and molecular (external)rotors in the energy-transfer mechanism are reported.II.Quasiclassical trajectory calculationsA.Intermolecular potentialThe lack of knowledge of the detailed form of intermolecular potentials has always been a hindrance to quasiclassical mod-elling of CET.This is especially true for large-substrate systems,where there is a paucity of reliable theoretical and experimental data.Previous trajectory calculations of large molecules usually modelled the intermolecular potential by pairwise-additive atom Èatom potentials:7h 24,48h 50the inter-action parameters were usually obtained by semiempirical methods.Collins and coworkers have ““builtÏÏintermolecular potentials by interpolation of ab initio data:51h 53thus far they have only applied their method to relatively small polyato-mics whereas we wish to use a protocol that can be consistent-ly and easily ““scaled upÏÏfor larger alkane systems.Hence in this work three pairwise-additive atom Èatom intermolecular potentials were employed.The Ðrst intermolecular potential was the pairwise-additive Lennard-Jones (LJ)potential with atom Èatom terms given by V ij \4e ijCA p ij r ij B 12[A p ij r ijB 6D,(1)(i \C,H;j \rare gas),where is the atom Èatom centre-of-r ijmass separation,and and are the Lennard-Jones radiusp ij e ijand well depth,respectively.The LJ parameters were chosen by the method of Lim to match empirical values.16,29,54The second intermolecular potential was the pairwise-additive Buckingham exponential (exp-6)potential with atom Èatom terms given byV ij \A ij exp([c ij r ij )[C ij r ij~6,(2)where the parameter determines the repulsive steepness ofc ijthe potential.55The parameters and were chosen toA ij C ijmatch empirical values.16,29,54The last intermolecular potential was a pairwise-additive hard-sphere (HS)potentialV ij \GO ,0,r ij O r ij vdW ,r ij [r ijvdW ,(3)where is the van der Waals radius 56between atoms i andr ijvdW j .This potential is in the spirit of the e†ective mass theory.57The HS potential is tested here to determine if it can be used to derive useful qualitative information:if so then it would be a useful model for simulations of larger alkanes.The intermolecular parameters for propane ]Rg (Rg \rare gases He,Ne and Ar)potentials are given in Table 1.B.Intramolecular potentialA simple harmonic valence force Ðeld,consisting of harmonic stretches,bends and torsions,was used to describe the propane substrate:V intra\;i V stretch,i ];i V bend,i ];iV torsion,i .(4)The Ðrst two terms have been deÐned previously.15,58,59The harmonic stretching and bending force constants were obtained by the empirical prescription of Lindner:60k str,CC\4.705]102J m ~2,J m ~2,k str,CH \4.702]102k bend,CCH\6.67]10~17J rad ~2,and J rad ~2.k bend,HCH\5.61]10~17The Ðnal term in eqn.(4)is a 3-fold methyl torsional potential,which was assumed to be:V torsion,i \V 0n ;j /1n cos 2A 3qij 2B.(5)The torsional angles are the nine H ÈC ÈC ÈH or H ÈC ÈC ÈCq ijdihedral angles for each of the i th C ÈC bonds.Each carbon centre was assumed to have perfect tetrahedral geometry with C ÈC and C ÈH bond lengths of 0.1543nm and 0.1093nm,respectively.To study the e†ect of the torsion,the torsional barrier parameter was taken to be 0(free rotors)and 13.8V 0kJ mol ~1(experimental barriers).61The direction of the bond vectors was deÐned so that the staggered conformer has the lowest-energy geometry.The free-rotor model has apparent harmonic torsional ““vibrationalÏÏfrequencies of 9.2and 9.3cm ~1while the hindered-rotor model has apparent harmonic torsional ““vibrationalÏÏfrequencies of 167.4and 186.3cm ~1.These fre-quencies arise from the numerical normal mode analysis and are used in the selection of initial conditions.58,59,62The other 25vibrational frequencies compare favourably with experi-mental group frequencies of putational detailsTrajectory calculations were performed using program MARINER 58which is a customised version of VENUS96.59The LJ and exp-6potential models,selection of initial condi-tions,and general methodology are standard options in program MARINER/VENUS96.58,59,62The initial impact energy was chosen from a 300K thermal distribution.InE transthe majority of cases,the initial rotational angular momentum of propane was chosen from a thermal distribution at 300K.The rotational temperature was varied from 100to 1500K to investigate the RET of propane ]argon by the HS model.The initial vibrational phases and displacements were chosen from microcanonical ensembles at E @\41000,30000or 15000cm ~1,where E @is the rovibrational energy above the zero-point energy.These initial conditions are appropriate for comparison with the Ðrst few collisions in time-resolved infra-red Ñuorescence and ultraviolet absorption experi-ments.3h 6,29h 38,64Note that experiments measure the CET values of a cascade of collisions.The rovibrational energy dis-tribution of subsequent collisions will not be microcanonical,Table 1Intermolecular potential parametersLJ model exp-6model HS model p (e /k B )Aij Cij c ij r vdW /nm/K /kJ mol ~1/10~6kJ mol ~1nm 6/nm 1/nm H ÉÉÉHe 0.28258.0882294712479.945.50.325C ÉÉÉHe 0.291517.6931859254179745.60.345H ÉÉÉNe 0.293817.00103476168.5345.70.305C ÉÉÉNe 0.302034.156********.6945.90.325H ÉÉÉAr 0.306628.87140033519.240.80.335C ÉÉÉAr0.321658.025809650187641.00.3551386Phys .Chem .Chem .Phys .,2000,2,1385È1392but the CET behaviour of these subsequent collisions can be inferred 18,65,66from the microcanonical values.For the models employing the LJ and exp-6intermolecular potentials,trajectories were initialised with a centre-of-mass separation of 1.2nm and the classical equations of motion were integrated by the Adams ÈMoulton algorithm 58,59,62until the distance between the monatomic collider and the closest hydrogen exceeded a critical value of 1.0nm,at which point the trajectory was terminated.The initial impact param-eter b was chosen with importance sampling 16,17,58,59,62for values between 0nm and nm (He and Ne)or 0.9nmb m\0.8(Ar).These initial and Ðnal conditions were chosen by per-forming preliminary runs which showed that an insigniÐcant amount of energy was transferred at larger distances.For the HS interaction model,there is no intermolecular interaction until the point of impact,when the propane sub-strate is still described by a (near)microcanonical putationally,this is achieved by initialising trajectories as above,but translating the colliders to the point of initial contact without altering the rovibrational phases and orienta-tion.The translation was performed using an algorithm devel-oped by Alder and Wainwright 67,68to model hard-sphere Ñuid systems.After this initial point of contact,the trajectory was propagated normally.At each time step,the interatomic distances between the rare gas collider and every propane atom were checked for overlap.If an atom Èatom encounter occurred,the trajectory was projected back to the point of impact and the impulsive momentum transfer was calcu-lated.68The process was repeated until another encounter occurred or until the distance between the monatomic collider and the closest hydrogen exceeded a critical value,at which point the trajectory was terminated.Program MARINER 58was altered to implement the HS potential and trajectory-propagation algorithms.The short-ranged HS interaction per-mitted critical values as low as 0.4nm.Since the equations of motion are integrated for a comparatively short period,the HS model required much less computing time than the LJ and exp-6models.For E @\15000and 30000cm ~1,the integration time step was chosen to be 0.085fs,which is sufficient to conserve total energy to within 0.5cm ~1.This is approximately four times larger than the time step used in our previous ethane trajec-tory calculations.24Propane has less excitation per vibra-tional mode and hence energy can be conserved by larger time steps.For E @\41000cm ~1,it was necessary to employ a time step of 0.075fs to conserve energy.The numerical insta-bilities associated with the inversion of the methyl group(s)previously observed in simulations of ethane 24and toluene 16,17were not observed here.The calculations were performed on a DEC Alpha 3000/300LX workstation and an SGI Power Challenge Super-computer.In calculations that employed the LJ or exp-6intermolecular potentials,batches of 3000trajectories required approximately 60CPU hours for He collider and 100CPU hours for Ar on the workstation.The HS model decreased the required CPU time by a factor of 10:this reduction will be very signiÐcant in the study of larger alkanes.CPU time was reduced by a factor of about 4on the supercomputer.D.Rotation energy and torsional angular momentum It is well documented that rotational energy transfer is an effi-cient pathway for CET.3,24,65,66,69However,while angular momenta are well-deÐned,rovibrational coupling gives rise to an ambiguity in the deÐnition of rotational energy.Previous quasiclassical simulations employed several di†erent methods to decouple the rotational and vibrational energies.One method 11deÐnes the rotational energy asE rot \1(JI ~1J ),(6)where I and J are,respectively,the instantaneous moment of inertia and angular momentum.In a second method isE rotapproximated by the instantaneous angular momentum,but the moment of inertia is taken to be the equilibrium geometry value.11Both deÐnitions give rotational energies that oscillate with time.There is an alternative deÐnition that is valid for symmetrical top rotors:65E rot \1B effJ 2,(7)where J is the magnitude of the rotational angular momentum and is an e†ective rotational constant.This deÐnitionB effdecoupled the rovibrational energy so that the rotational energy includes only the ““adiabatic partÏÏ,whereas the ““activeÏÏpart is included with the vibrational energyE V \E [E rot,(8)where and E are,respectively,the vibrational and totalE Vinternal energies.Eqn.(7)is a valid approximation for sym-metrical top molecules.70The main advantage of this deÐni-tion is that,classically,it is a conserved quantity.The equilibrium Cartesian principal moments of inertia of propane are kg m 2,kgI xx \1.11]10~45I yy\9.7]10~46m 2and kg m 2.Hence,propane is a goodI zz\2.97]10~46approximation of a symmetrical top and it is possible to deÐne the rotational energy by eqn.(7),with the approx-imationB eff \12hc (I xx I yy I zz)~1@3.(9)It was shown in our previous work on ethane 24that the coupling between external and internal rotors enhances the overall CET.Hence the torsional angular momentum of propane was also monitored in this work.Whereas ethane has only one torsional rotor which lies along its molecular axis,propane has two distinct and unparallel torsional rotors.The deÐnition of the torsional angular momentum introduced for ethane is generalised by calculating the rotational angular momentum of the methyl group and the associated ethyl groupJ methyl \;i /H,H,Hr i ]p iJ ethyl\;i /C,H,Hr i ]p i,(10)where is the angular momentum of the methyl groupJ methyland is the angular momentum of the associated ethylJ ethylrotor.Note that for consistency with eqn.(5),only the six atoms directly bonded to each torsional C ÈC bond have been included in the summation in eqn.(10).The torsional angular momentum is then deÐned asJ tor \o (J methyl [J ethyl)Éa o ,(11)where is a unit vector parallel to the CC torsional axis.The a CET to/from the torsional rotors was monitored by calcu-lating the average torsional angular momentum change*J tor \J tor (Ðnal)[J tor(initial).(12)E.Data analysisTrajectory data were analysed by a bootstrap algorithm 71,72in program PEERAN.16,73Some 3000È5000trajectories were performed for each potential model.This was sufficient to obtain average energy-transfer quantities with statistical uncertainties of about 10%.However,the uncertainties for the average rotational energy transfer were about 20%,due to the initial rotational-energy Boltzmann distribution (rather than an initial microcanonical distribution).Trajectory averagesPhys .Chem .Chem .Phys .,2000,2,1385È13921387deÐned by (for both overall CET and RET)S*E n TtrajS*E n T traj \1N ;i /1N bi bm(*E i )n(13)are related to experimentally obtained quantities S*E n T by ratio of collision cross-sectionsS*E n T \p b m 2p p LJ2X (2,2)RS*E n T traj (14)where is the LJ collision cross-section and is thep LJ 2X (2,2)R b mmaximum impact parameter in the trajectory simulation.This normalisation removes the ambiguity related to the elastic scattering at high impact parameter.74The input LJ param-eters were obtained from ref.29.At 300K,the LJ collision cross-section values of nm 2,0.4834nm 2p LJ2X (2,2)R \0.3976and 0.6945nm 2for propane ]He,propane ]Ne and propane ]Ar,respectively,were obtained using the program COLRATE.75This corresponds to the LJ collision frequencies of m 3s ~1,328.58]10~18m 3s ~1Z LJ,coll\523.29]10~18and 382.37]10~18m 3s ~1,respectively.In this paper,we have reported both the Ðrst and second moments of the trajectory data since the Ðrst moment is usually more useful for comparison with experiment,but the QCT second moment is statistically more reliable.74Some experiments can determine both the Ðrst and second moments of the CET probability.3,5III.Results and discussionA.The e†ect of the torsional barrierFigs.1and 2show the CET values,[S*E T and S*E 2T 1@2,and the RET values,as functions of energy E @aboveS*E RT ,zero-point energy for propane ]neon.One set of results areFig.1Dependence of energy-transfer quantities on torsional barrier for deactivation of vibrationally excited propane by neon bath gas:)Hindered-rotor (LJ);Free-rotor (LJ);Hindered-rotor (exp-6);L +…Free-rotor (exp-6).Fig.2Dependence of rotational energy transfer on torsional barrier for deactivation of vibrationally excited propane by neon bath gas:)Hindered-rotor (LJ);Free-rotor (LJ);Hindered-rotor (exp-6);L +…Free-rotor (exp-6).for the free-rotor model the other for the hindered-(V 0\0),rotor model kJ mol ~1).These results are for the LJ(V 0\13.8and exp-6intermolecular potentials.The overall deactivation,[S*E T and S*E 2T 1@2,is larger for the hindered-rotor model,similar to results for ethane ]neon.24The torsional angular momentum transfer is shownS*J torT in Fig.3.Note that for the hindered-rotor modelsS*J torT with both LJ and exp-6intermolecular potentials are virtually identical:the reason for this is unclear.Overall,S*J torTdecreases,but remains positive,with the presence of a barrier In contrast,for ethane ]neon changes from posi-V 0.S*J torT tive to negative over a similar range of values.24This di†er-V 0ence is probably due to the higher torsional moment of inertia for propane torsion compared to ethane(CH 3ÈCCH 2)This means that propane torsion has higher(CH 3ÈCH 3).density of states and can more readily gain torsional excita-tion than ethane torsion,explaining why is positiveS*J torT for propane,but negative for ethane.In ethane,the torsion acts like a vibration providing an efficient torsion ]T pathway.24The increase in [S*E T and S*E 2T 1@2(Fig.1)for the hindered-rotor model suggests that propane torsions play the same role in the CET mechanism.The RET is smaller for the propane free-rotor modelS*E RT than the hindered-rotor model (Fig.2),contrary to the ethane results.24For ethane,the torsion is aligned along the molecu-lar axis,hence any increase in methyl-rotor angular momen-tum contributes to both (internal)torsional excitation S*J torTand (external)rotational excitation The propane free-S*E RT .rotor model has Ðve (three external and two internal)indepen-Fig.3Dependence of torsional angular momentum change on tor-sional barrier for deactivation of vibrationally excited propane by neon bath gas:Hindered-rotor (LJ);Free-rotor (LJ);)L +Hindered-rotor (exp-6);Free-rotor (exp-6).Note that the two sets …of hindered-rotor results are almost identical.1388Phys .Chem .Chem .Phys .,2000,2,1385È1392dent rotors,none of which have coincident axes.The extra rotors mean that there is less energy available to the external rotors in any V ]torsion,R energy redistribution.Noteworthy is the fact that the di†erences between the free-rotor and hindered-rotor models persist up to E @\41000cm ~1.For ethane ]neon,there is an onset of near-free-rotor behaviour at E @\30000cm ~1:at E @\41000cm ~1there is no signiÐcant di†erence between the free-and hindered-rotor models.However,the larger number of vibrational modes in propane,which decreases the excitation per torsional mode,ensures that the di†erences remain even at very high excita-tion.Hence correct theoretical treatments of internal rotors become even more essential for larger molecules.B.Trajectory results for LJ and exp-6modelsThe CET results for the deactivation of highly excited propane by helium,neon and argon are shown in Fig.4,where the intermolecular interactions have been modelled by the LJ and exp-6potentials.Three important features are:(1)Energy transfer increases with increasing E @and is in accord with theoretical and experimental studies on the deac-tivation of highly vibrationally excited molecules.(2)The LJ potential results in larger CET values than the exp-6model,since the LJ potential has a much harder repul-sive part than the exp-6potential.There are numerous works which concluded that CET depends mainly on the repulsive part of the intermolecular potential and that,in general,a harder repulsive part results in larger energy transfers.9,16,17(3)The deactivator efficiency shows the trend He [Ne [Ar which,unfortunately,is in discord with experi-mental trends for Ñuorinated alkane systems.28To our knowledge,there has been no experimental study of CET in propane ]rare gas systems.““IndirectÏÏstudies of related systems include 2-bromopropane ]Ne ([S*E T \130cm ~1for E @\17000È21000cm ~1)76andFig.4Energy-transfer quantities for deactivation of vibrationally excited propane by rare gases:Helium (LJ);Neon (LJ);)K |Argon (LJ);Helium (exp-6);Neon (exp-6);Argon (exp-6).+=>isotopically-substituted cyclopropane ]He (S*E 2T 1@2\200È400cm ~1for E @D 22000cm ~1).2These CET quantities were not directly measured,but were inferred from pressure-dependent thermal reaction rates at elevated temperatures.Some more recent studies using time-resolved optoacoustic spectroscopy include ([S*E T \114cm ~1atC 3F 8]Ar E @\15000cm ~1and [S*E T \300cm ~1at E @\40000cm ~1).46These studies reveal no information about RET nor the role of torsional modes.These experimental CET quan-tities correlate well with our present calculations (Fig.4)but also indicate a need for fresh experimental studies.The decreasing trend with collider He [Ne [Ar has been observed in many other QCT studies.9,15,18,77Although the lack of qualitative agreement with experiment is disappoint-ing,these studies and the present work have used very crude intermolecular potential models.Given the lack of detailed information about polyatomic intermolecular potential sur-faces,the intention in the present and other studies has been to use a set of consistent and transferable potentials,16much in the spirit of molecular mechanics force Ðelds.Experience with simulations on other systems would suggest that the exp-6model potentials predict ““betterÏÏCET values than the LJ potentials.17Fig.5plots the RET of propane ]rare gas systems.For Ne and Ar,monotonically increases with E @,whereas forS*E RT He,it initially increases but decreases at higher excitation energy.In all cases,RET is larger for the LJ model which is in accord with the CET behaviour.Clary and Kroes 78and others 16,17,40have observed that RET is larger for heavier colliders because the collision duration is closer to the rota-tional period of the molecular substrate.Fig.6plots the torsional angular momentum transfer as a function of E @.is largest for He and smal-S*J tor T S*J torT lest for Ar,which is the same trend as for CET.This implies that,in addition to the external rotor gateway,the torsional rotor is a gateway for facile CET via V,torsion ]torsion,T.24An interesting feature of Fig.6is that seems to beS*J torT Fig.5Rotational energy transfer for deactivation of vibrationally excited propane by rare gases:Helium (LJ);Neon (LJ);)K |Argon (LJ);Helium (exp-6);Neon (exp-6);Argon (exp-6).+=>Phys .Chem .Chem .Phys .,2000,2,1385È13921389Fig.6Torsional angular momentum change for deactivation ofvibrationally excited propane by rare gases:Helium(LJ);Neon)K(LJ);Argon(LJ);Helium(exp-6);Neon(exp-6);Argon|+=>(exp-6).insensitive to the intermolecular potential.However,the factthat it depends on the type of bath gas indicates a dependenceon the mass of the deactivator.This suggests that isS*JtorTinsensitive to theÐne details of the intermolecular potentialand can be modelled by either LJ or exp-6potentials.C.Trajectory results for hard-sphere modelLJ and exp-6potentials have long-range attractive terms andare computationally expensive.Since HS is a short-rangepotential,it is computationally cheaper in terms of computertime than other potential models by an order of magnitude.Inthis section we compare the results of the short-range HS withthe longer-range potentials.Fig.7shows S*E T and S*E2T1@2for the HS model.Fig.8shows the RET for the HS model.The qualitative behavioursare the same as for the LJ and exp-6models but the energy-transfer values are several times larger than for the LJ andexp-6model.This is not surprising in view of the““hardnessÏÏof the HS potential.9,16,17Another important feature is thatS*E T and S*E2T1@2for He are several times larger than forNe and Ar.This is also true for the LJ model(Fig.3)whichindicates that the HS and LJ models tend to give CET valuesthat are much too high for helium colliders.Table2lists the average number of encounters per collision,for He,Ne and Ar colliders.This average includes onlyNC,trajectories in which collisions have occurred.As expected NCTable2Average number of atomÈatom encounters NcE@/cm~1150003000041000Propane]He 1.967 1.884 1.847Propane]Ne 3.145 2.952 2.852Propane]Ar 3.753 3.501 3.400Fig.7Energy-transfer quantities for deactivation of vibrationallyexcited propane by rare gases for the HS model:Helium;Neon;+=Argon.>is largest for Ar and smallest for He due to their reducedmasses.also decreases with increasing E@which suggestsNCthat a more highly excited substrate imparts more energy perencounter to the deactivator,reducing the collision duration.Fig.9shows S*E T,and for propane]argonS*EVT S*ERTsystems at rotational temperatures300,1000andTROT\100,1500K.In these simulations,initial excitation wasÐxed atE@\15000cm~1and the initial translational temperaturewas K.It can also be seen that RETTtrans\300S*ERTdecreases with increasing the magnitude of the vibra-TROT;tional energy transfer also decreases with increasingS*EVTThis implies that rotationally cold systems exhibitTROT.V]R,T energy transfer,whereas rotationally hot systemsexhibit V,R]R,T.It can be seen that the overall[S*E T islarger for larger which agrees with the hypothesis thatTROTthe external rotation is a facile CET path.This behaviour hasFig.8Rotational energy transfer for deactivation of vibrationallyexcited propane by rare gases for the HS model.Helium;Neon;+=Argon.>1390Phys.Chem.Chem.Phys.,2000,2,1385È1392。

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a r X i v :a s t r o -p h /9909496v 1 29 S e p 1999A&A manuscript no.(will be inserted by hand later)ASTRONOMYANDASTROPHY SICSSend oﬀprint requests to :L.Spinoglio,luigi@r.it ⋆Based on observations with ISO,an ESA project with in-struments funded by ESA Member States (especially the PI countries:France,Germany,the Netherlands and the United Kingdom)with the participation of ISAS and NASAThe estimated relatively high density and compact-ness of the observed emission suggest that it originates from the shocks taking place at the base of the molecu-lar outﬂow emission,in the region where the action of the stellar winds from the two stars of the binary system is important.Key words:Stars:formation;Stars:individual:T Tau;Stars:pre-main sequence;ISM:individual objects:T Tau;ISM:jets and outﬂows;Infrared:ISM:lines and bands2L.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau mapped by Edwards&Snell(1982)in12CO J=1-0andJ=2-1,who found that95%of the high velocity molec-ular gas is associated with blueshifted material.The di-rection of the detected outﬂow is roughly parallel to theline of sight,but the emission also shows a region extend-ing2arcmin to the south and east of T Tau N with asecondary peak in the blueshifted wing.Higher resolution maps of the12CO J=3-2,J=6-5and C18O J=1-0,J=2-1 and HCO+emission later showed(Schuster et al.1993, Momose et al.1996,Schuster et al.1997,Hogerheijde et al.1998)a complex outﬂow system that could originate from the diﬀerent components of the binary system.The fast stellar winds observed through forbidden opti-cal line emission(B¨o hm&Solf1994),revealedﬁve distinct kinematic components that suggest that both the primary star and the companion may drive separate bipolar out-ﬂows.A giant Herbig-Haroﬂow was recently discovered (Reipurth et al.1997)around T Tau and is interpreted as originating several thousand years ago from T Tau S.Strong and extended H2ro-vibrational emission was found quite early around T Tau(Beckwith et al.1978). Recently,high resolution H2imaging(Herbst et al.1996, 1997)indicated that the extended molecular hydrogen emission arises from the impact on the ambient cloud of two outﬂow systems oriented NW-SE and E-W.These originate from the two stars,each with its circumstellar disk,and the emission is distributed equally over T Tau N and T Tau S.Infrared adaptive optics observations in H2 show instead that the emission is concentrated on T Tau S and is interpreted in terms of shocks occurring as matter accretes onto the circumstellar disk of T Tau S(Quirren-bach&Zinnecker1997).Noﬁrm conclusion is therefore reached on this problem.T Tau has associated a substantial amount of mass of dust,it is therefore luminous in the millimeter continuum (Adams et al.1990,Beckwith et al.1990).A circumstellar disk has been detected both with CO interferometry and infrared scattered light(Weintraub et al.1989,Momose et al.1996).Later,millimeter continuum interferometry at0.9and3mm(Hogerheijde et al.1997,Akeson et al. 1998,respectively)was used to derive a total mass of0.04 M⊙for the circumstellar disk around T Tau N and at least10times smaller for that associated to T Tau S.A circumbinary envelope would also be required toﬁt the continuum energy distribution.Far-infrared spectroscopy provides powerful diagnostic lines from abundant molecular species like CO,H2O and OH,that can be used to clarify the physical processes at work in the complex T Tau system.In this paper we present the far-infrared spectrum observed from the Long Wavelength Spectrometer(LWS,Clegg et al.1996)on-board the Infrared Space Observatory(ISO,Kessler et al. 1996).Additional data from the Short Wavelength Spec-trometer(SWS,de Graauw et al.1996)are also used for discussing the molecular emission properties.The main results of the SWS are presented by van den Anckeret Fig.1.The complete ISO LWS and SWS spectrum of T Tau.The IRAS data are also shown for comparisonal.(1999).The continuum far-infrared spectrum of T Tau will be discussed in a forthcoming paper(Pezzuto et al.in preparation).2.ObservationsT Tau has been observed with ISO(Infrared Space Ob-servatory)using the LWS(Long Wavelength Spectrome-ter,Clegg et al.1996).A full low resolution(R∼200) spectrum of the source from45to197µm was obtained during revolution680,corresponding to September,25, 1997.The beamsize is on average80arcsec,depending on the wavelength.The spectrum was made up of23full grating scans oversampled at1/4of a resolution element, with each spectral sample integrated for11.5sec,with a total integration time of4265sec.Besides the observa-tion on-source,full grating spectra were also collected at four oﬀ-source positions.In Table1we present the jour-nal of the LWS observations,which includes source and oﬀ-source positions and total observing time(OTT).The raw data were reduced and calibrated using ver-sion7of the LWS pipeline,which achieves an absolute ac-curacy of about30%(Swinyard et al.1998).Post-pipeline processing was carried out with the ISAP package and in-cluded removal of spurious signals due to cosmic ray im-pacts and averaging the grating scans of each detector.Besides the data measured by the LWS,we also discuss in this paper the detection of H2O and OH emission lines observed by the SWS.The details of these observations are reported by van den Ancker et al.(1999).L.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau3Fig.2.The ISO-LWS emission line spectrum of T Tau,from which the continuum has been subtracted.3.ResultsThe 2-200µm far-infrared spectrum of T Tau composed by the ISO LWS and SWS spectra is shown in Fig.1.The displacement (of ∼15%)between the ﬂux level of the two instruments at ∼45µm is well within the calibration uncertainties.In the ﬁgure,IRAS photometry is also re-ported for comparison.As discussed in van den Ancker et al.(1999),the higher ISO ﬂuxes compared to the IRAS data (30-50%)can be explained by the ﬂare that occurredto the system in 1990-1991(Ghez et al.1991;Kobayashi et al.1994),after which the infrared luminosity of T Tau did not return to the pre-outburst value.The line spectrum (Fig.2)is very rich in molecu-lar emission lines from the rotational spectra of carbon monoxide,water and hydroxyl.The line ﬂuxes,computed by ﬁtting gaussian proﬁles to the lines,are listed in Tables 2-5.All of the CO transitions with J up =14-25appear in the spectrum.However,we cannot assign a ﬂux,but only4L.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau Table1.Journal of the ISO-LWS observations of T TauT Tau on4:21:59.4+19:32:06.54265 T Tau oﬀN4:21:59.4+19:33:46.51345 T Tau oﬀS4:21:59.3+19:30:26.51345 T Tau oﬀW4:22:06.4+19:32:06.01345 T Tau oﬀE4:21:52.4+19:32:07.01345λobs Line id.λvac F∆F(µm)(µm)(10−20W cm−2)Notes:†:wavelength wasﬁxed for deblending.⋆:this line is blended with the o-H2O414-303(see text),the totalﬂux has a1σuncertainty of0.5·10−20W cm−2.3.1.CO emissionFor the CO model,we computed the collisional downward rates for levels with J up<60and T>100K using theγJ0 coeﬃcients taken from McKee et al.(1982),while the up-ward rates were computed using the principle of detailed balance.Radiative decay rates were taken from Chacke-rian&Tipping(1983).The distribution of the observed CO lineﬂuxes as a function of the rotational quantum number is shown in Fig.3.Because the CO lines are optically thin,their emis-sion,in the LVG model considered,does not depend on the velocity gradient and thus on the assumed line-width. We have considered for ourﬁt only the transitions with J up less than22.Our data are consistent with gas tem-peratures ranging from T=300to900K and molecular hydrogen densities of n=105−6cm−3.The two extreme models consistent with the data have:T=300K and n H2=4·106cm−3;T=900K and n H2=2·105cm−3.Fig.3shows that the transitions with J up=24and25 have aﬂux level which is too high to be explained by the same gas component of the other lines and may indicate the presence of a warmer gas emission.This warmer com-ponent,which cannot easily be constrained by the higher J up transitions observed,could also aﬀect the J up=21 and22lines.Howeverﬁtting the component covering the lines14≤J up≤20,results in the same parameters as the low temperature model above.L.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau5 Fig.3.Modelﬁts through the observed CO lines.Therange of temperatures and densities compatible with theobservations are indicated.The higher observed J lines(J=24,25and26)haveﬂuxes too high to beﬁtted bythe same parameters as the other lines,suggesting thepresence of a second component.3.2.H2O emissionAs outlined in the previous Sect.,we adopted the temper-ature and density as derived from the CO lines models toﬁt the observed H2O lineﬂuxes.We considered in the computation45levels for boththe ortho and para species(i.e.excitation energies up to∼2000K):radiative rates are taken from Chandra et al.(1984)while the H2O-H2collision rates are derived fromGreen et al.(1993).We assumed an ortho/para abundanceratio of3,equal to the ratio of the statistical weigths oftheir nuclear spins.The other parameters that enter in the model are thevelocity gradient in the region(dV/dr)and the projectedarea of the emission region.The optical depth in thelines is directly proportional to the water column den-sity(N(H2O)).Since the ratios of diﬀerent lines dependon their relative optical depths,we can use them to con-strain dV/N(H2O).On the other hand,the absolute lineintensity depends on both the column density and theprojected area of the emission region,and therefore if weassume a velocity linewidth dV,we can estimate both thecolumn density and the emission region size.The results of the modelﬁtting are shown in Fig.4and Fig.5for ortho-and para-H2O respectively.Almostall the lines in the LWS wavelength interval are well re-produced by the model.The diﬀerences in theﬂuxlevelparison of the modeled ortho-H2O lineﬂuxes(ﬁlled triangles)with those observed(open circles)for thetwo modelsconsidered.parison of the modeled para-H2O lineﬂuxes(ﬁlled triangles)with those observed(open circles)for thetwo models considered.predicted in the two extreme models are quite small,indi-cating that the H2O emission is not very sensitive to theexact value of temperature and density in the range.Onthe other hand,we note that the ortho-H2O lines short-ward of50µm are notﬁtted by our models.These lines,6L.Spinoglio et al.:The shock excited far-IR molecular spectrum of T TauTable3.Measured water lineﬂuxes from the SWS(up-per list)and LWS(lower list)grating spectrum,with1σuncertainties.Upper limits are at3σ.25.940o-H2O541-41425.940 2.40.629.838o-H2O725-61629.836 4.9 1.1o-H2O441-31231.771<3.040.342o-H2O643-53240.337 5.7 1.340.688o-H2O432-30340.68814.1 2.643.894†o-H2O541-43243.8947.8 1.545.116o-H2O432-30345.111 5.8 1.9 Notes:†:wavelength wasﬁxed for deblending.⋆:this line is blended with the CO23-22line(see text),the totalﬂux has a1σuncertainty of0.5·10−20W cm−2. originated by levels at energies higher than500K,are brighter than our predictions,indicating that a warmer component might be required,as also suggested from thehigher J CO lines.An estimate of the intrinsic linewidth dV can be given if we relate the observed emission with the outﬂow/wind activity taking place in the close environment of the T Tau binary system.The molecular outﬂow has been traced by diﬀerent lines at near infrared and millimeter wave-lengths(H2,CO,HCO+),showing linewidths of a few km s−1.Adopting a velocity of10km s−1,close to the out-ﬂow velocities of7.9km s−1(red lobe)and9.7km s−1(blue lobe)measured by Levrault(1988)and those measured by Hogerheijde et al.(1998)in13CO3-2(of12.and15.6km s−1for the red and blue lobes,respectively),we derive a water column density of(2-5)1017cm−2,while the pro-jected area is(4-9)arcsec2.This corresponds to a diameter of only300-400AU,assuming spherical simmetry.The compactness of this emission region will enable us to put constraints on the physical mechanisms responsible of the observed emission(see Sect.4)parison of the modeled OH lineﬂuxes(ﬁlled triangles)with those observed(open circles).Using this emission area,the CO column density that we derive from the observed CO absolute lineﬂuxes is N(CO)=(0.7-2.0)1018cm−2and therefore an H2O/CO abundance ratio of∼0.1-0.7.Assuming a standard CO abundance of10−4,the water abundance with respect to H2is∼(1-7)·10−5.This value implies an enhancement with respect to the expected abundance in the ambient gas of at least a factor of10(e.g.Bergin et al.1998).High H2O abundances are common in young stellar objects:the ISO spectrometers have in fact found strong emission from gas-phase H2O from massive young stars (Harwit et al.1998,Gonz´a lez-Alfonso et al.1998)and from low mass outﬂow driving sources(Liseau et al.1996, Saraceno et al.in preparation,Ceccarelli et al.1998)with abundances in the range1-5·10−5,rising to values as high as∼5·10−4in L1448mm(Nisini et al.1999b)and Orion (Harwit et al.1998).3.3.OH emissionFor the OH models,we have considered20levels.The collisional downward rates are from Oﬀer&van Dishoeck (1992)and the radiative decay rates are from the HITRAN catalogue(Rothman et al.1987).If we adopt the same parameters as derived from the above analysis also for the OH,weﬁnd that a better agree-ment between data and models is achieved with the lower temperature model(T=300K).The estimated OH col-umn density is N(OH)∼4·1017cm−2and therefore a X(OH)∼2.7·10−5.The results of the OH modelﬁttingL.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau7 Table 4.Measured OH lineﬂuxes from the SWS(upper list)and LWS(lower list)grating spectrum,with1σuncertainties.Upper limits are at3σ.28.9310.020OH2Π1/27/2-2Π3/25/228.939 2.70.9OH2Π1/25/2-2Π3/23/234.603/34.629<6.443.950†0.045†OH2Π1/27/2-2Π3/27/243.950 5.2 1.5Notes:†:wavelength wasﬁxed for deblending.are shown in Fig.6.As can be seen from thisﬁgure,not all the lines can be reproduced by the models,in particular both the163µm line and those shortward of60µm.Because T Tau is relatively bright in the continuum at the far infrared wavelengths(see Fig.1),such a discrep-ancy could be due to the pumping from the local ther-mal radiationﬁeld.To test this possibility we also com-puted models for the OH transitions including theﬁeld originated from dust at a temperature of300K,using the model of Cesaroni&Wamsley(1991).We found that the inclusion of the local infrared radiationﬁeld increases the emission in the lines withλless than100µm and the 163µm line.3.4.Atomic emissionThe detection of[CII]158µm in the four oﬀ-source posi-tions around T Tau(see Table5)clearly shows that most of the ionized carbon emission(∼80%)is from an ex-tended region and not originated in the vicinity of T Tau. The intrinsic emission in the LWS beam centered on T Tau is about2·10−20W cm−2.This implies a ratio [OI]63µm/[CII]158µm of115,greatly in excess of that expected from photodissociation region models(Kaufman et al.1999;Burton et al.1990).Finally the ratio of[OI]63µm/145µm=28.3is such that no oxygen self-absorption should occur,as it often appears to be the case towards pre-main sequence sources(Sara-ceno et al.1998).This suggests that there is no cold gas in front of the source,in accordance with the geometry of the outﬂow directed towards the observer.As outlined in van den Ancker et al.(1999),based on a larger set ofﬁne-structure lines detected at shorter wave-lengths,we argue that the atomic line emission observed is consistent with the presence of J-type dissociative shocks. On the other hand,the excess[CII]158µm emission on-source could also be due to a local photodissociation region (PDR),possibly originated from the far-UVﬁeld of T Tau (see Sect.4).3.5.Total coolingTable6summarises the physical quantities derived from the observed molecular spectra of CO,H2O and OH, adopting the two models considered:the column densi-ties and the total cooling luminosities are given for each molecular species.We also give the observed values of the cooling derived from the sum of all the detectedﬂuxes.For deriving L H2,we used the lineﬂuxes reported in van den Ancker et al.(1999)and the line H21-0S(1)at2.12µm, given in Carr(1990).A comparison between the observed and modeled cooling shows that the observations of CO, H2O and OH can account for most of the modeled cooling. The underestimate of the OH cooling by the900K model conﬁrms that this latter is probably inadeguate to explain the observed OH emission.The total radiated cooling ob-served from these species,including[OI],sums up to about 0.04L⊙,and has to be considered as a lower limit.Tak-ing the outﬂow parameters from the literature(Levreault 1988;Mundt1984)we derive a total mechanical luminos-ity of about0.05L⊙(we have taken an average veloc-ity of10kms−1,a total outﬂow mass of0.22M⊙,and a dynamical timescale of40,000years).The radiative lumi-nosity observed in the far-infrared is therefore comparable to the outﬂow mechanical luminosity.This is expected if the stellar winds from the stars are driving the outﬂows and the shocks,traced by the far-infrared lines,accelerate8L.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau Table5.Measured atomic lineﬂuxes from the LWS grating spectrum with uncertainties.on63.21[OI]3P1→3P263.18230.6 1.0on145.52†[OI]3P0→3P1145.528.150.78on157.76[CII]2P3/2→2P1/2157.7410.60.5oﬀ-N157.80[CII]2P3/2→2P1/2157.747.90.7oﬀ-S157.79[CII]2P3/2→2P1/2157.748.8 1.2oﬀ-W157.76[CII]2P3/2→2P1/2157.748.80.9oﬀ-E157.74[CII]2P3/2→2P1/2157.749.10.7observed⋆“lower T”“higher T”Notes:⋆:The observed cooling is computed by summing allthe detected lines.4.DiscussionOnce the physical conditions of the emitting gas in the vicinity of T Tau have been established,we can now pro-ceed to compare the results with existing models of shock excitation.The far-infrared line emission of young stel-lar objects is mainly originated from two physical pro-cesses:the excitation from photoionized and photodisso-ciated(PDR)regions(Tielens&Hollenbach1985)and the shock excitation produced by the interaction of su-personic winds with the ambient medium.Depending on wind velocity,magneticﬁeld and ion density,two kinds of shocks with diﬀerent far-infrared spectra are predicted from models:i)high velocity dissociative J shocks(e.g.Hollenbach&McKee1989),in which temperature,density and veloc-ity have a discontinuous jump(J)on the shock front, molecules are dissociated and atomic lines are the dom-inant coolants;ii)low velocity non-dissociative C shocks(e.g.Kaufman &Neufeld1996,Draine et al.1983)in which the ion Alfv´e n velocity is larger than the shock velocity and the magneticﬁeld transmits energy faster than the shock velocity;in this case temperature,density and velocity have a continuous(C)variation and molecules are the dominant coolants.Instead of using intensities of many tens of diﬀerent lines,we can obtain a better comparison between our data and the shock model predictions using the total cooling from a single species.In Fig.7we show the water cooling as a function of the[OI]63µm cooling,both normalized to the high-J CO cooling.The C-type shock models of Kaufman&Neufeld (1996)are considered.The J-type shock models(Hollen-bach&McKee1989)are also indicated(seeﬁgure caption for details).Together with the position of T Tau,we also show in thisﬁgure the positions of L1448(Nisini et al. 1999b),IC1396(Saraceno et al.1999),IRAS16293-2422 (Ceccarelli et al.1998),and the Herbig-Haro objects HH54 (Liseau et al.1996),HH25and HH26(Benedettini et al. 1998).T Tau is in a central position,showing that both C-type and J-type shock models could explain the obser-vations.It has to be noted,however,that according to Kaufman&Neufeld models,its position implies a shock velocity between10and15km s−1,in a range where wa-ter production is triggered but it is not at its maximum eﬃciency.We can see in theﬁgure that other pre-main sequence sources also cluster in the same region of T Tau, indicating that these shock conditions are fairly common in the environment of young stellar objects(Nisini et al. 1998).Fig.8shows the water cooling as a function of the OH cooling,both normalized to the high-J CO cooling.As before,we consider both J-type and C-type shocks.The position of T Tau in this plot appears to be consistentL.Spinoglio et al.:The shock excited far-IR molecular spectrum of T Tau9 Fig.7.Total cooling from water lines versus[OI]63µm cooling,both normalized to the CO(high-J)cooling in few objects,including T Tau(ﬁlled triangles)and according to shock models.The open triangle showsthe position that T Tau would have if the water coolingwere increased by a factor3.C-type shock models ofKaufman&Neufeld(1996)are shown in a grid whereshock velocity increases from the right to the left from10<v s<40km s−1(dashed lines)and density from thebottom to the top from104to106.5cm−3(solid lines).J-type shock models(Hollenbach&McKee1989)are shownfor comparison as large dashed circles,where S is thestandard model,with preshock density of n o=105cm−3,shock velocity of v s=80km s−1and magneticﬁeld ofB=158µG;UV-:the far-ultravioletﬁeld is reduced by afactor of10;B-:the magneticﬁeld is reduced by a factor10;B+:the magneticﬁeld is increased by a factor10;GR-:the grain size distribution is extended down to10˚A;HL:H2formation on grains is equal to zero;HZ:H2formation heating is set to zero.with J-type shocks.The main reason why C-shocks failto reproduce the observed cooling is the overabundance ofOH molecules,by at least a factor10.Only a model whichincludes the eﬀects of the presence of a high UVﬁeld fromT Tau itself can reproduce the observed values.Fig.9shows the water cooling as a function of the H2cooling,both normalized to the high-J CO cooling.T Taulies exactly in the center of the region of C-type shocksand cannot be explained by J-type shocks.As expected,the strong H2emission cannot be accounted for by J-typeshocks.We therefore rule out the hypothesis that the ma-jor responsible of the observed excitation areJ-shocks.Fig.8.Total cooling from water lines versus total coolingfrom OH lines,both normalized to the CO(high-J)cool-ing in few objects,including T Tau(ﬁlled triangles)andaccording to shock models.The open triangle shows theposition that T Tau would have if the water cooling wereincreased by a factor3and the OH cooling decreased bya factor10.C-type shock models of Kaufman&Neufeld(1996)are shown in a grid as a function of density andshock velocity.J-type shock models(Hollenbach&Mc-Kee1989)are shown as large dashed circles(see captionof Fig.7).Because photodissociation of water by an UVﬁeld,that is not included in shock models,can convert waterto OH,we suppose that the overabundance of the OHmolecule is due only to the strong far-UV radiationﬁeldassociated to T Tau(Herbig&Goodrich,1986).The pho-todissociation cross Sect.of water at the Lyαfrequency isin fact ten times larger than the one of OH(van Dishoeck&Dalgarno1984).A similar situation has been found insupernova remnants,where OH1720MHz emission is ex-plained as originated from C-type shocks,allowing thatthe action of an UVﬁeld creates suﬃcient OH from waterdissociation(Wardle et al.1998;Lockett et al.1999).If this is the case,the far-infrared molecular emissionspectrum of T Tau is primarily due to C-type shocks.Toreconcile the OH observations with C-type shock modelswe need that the OH abundance,and thus its total cooling,were reduced by a factor10in favor of water cooling.FromTable6,if we reduce by a factor10the OH column densityand we increase of the corresponding amount that one ofthe water,passing from2·1017to5.6·1017,we will increasethe total water cooling by a factor of about3.10L.Spinoglio et al.:The shock excited far-IR molecular spectrum of TTauFig.9.Total cooling from water lines versus total cooling from H 2lines,both normalized to the CO (high-J)cooling in T Tau and L1448(Nisini et al.1999b)(ﬁlled triangles)and according to shock models.The open triangle shows the position that T Tau would have if the water cooling were increased by a factor 3.C-type shock models of Kauf-man &Neufeld (1996)are shown in a grid where density increases upward and shock velocity from the left to the right.J-type shock models (Hollenbach &McKee 1989)are shown as large dashed circles (see caption of Fig.7).Increasing the water cooling by this factor and de-creasing the OH cooling by a factor 10would move the position of T Tau in the three diagrams of Fig.7,8and 9in positions fully consistent with C-type shock mod-els (see the open triangles in the ﬁgures),at pre-shock densities of about 105.5−6cm −3and shock velocities of 10<v s <20km s −paring the pre-shock densities of these models with the densities derived from our LVG models,we found that a moderate compression factor (≤10)would be required.In support of the fact that the molecular emission is due to C-type shocks is the evidence of the presence of strong magnetic ﬁelds in the outﬂow re-gion associated with T Tau S (Ray et al.1997).Our conclusion that the observed far-infrared molec-ular emission from T Tau can be explained by C-type shocks and that the atomic emission is probably origi-nated in J-type shocks is in agreement with the ﬁndings of van den Ancker et al.(1999).Their models,based on the near to mid-infrared H 2emission imply two temper-ature components at 440K and 1500K,which again are roughly in agreement with our ﬁnding of two components:one ranging from 300K to 900K and another at an higher temperature traced by the higher J up CO transitions.As to the origin of the C-type shocks,responsible for the observed far-infrared molecular emission,we know from the LVG models that the emission region has a size of only few hundreds AU,assuming a spherical geometry.This implies that the shocks occur in a very compact re-gion,presumably very close to the binary system.There are at least three mechanisms not mutually exclusive to explain the origin of the shocks:1.from the interaction region of winds coming from the two stars;2.from disk accretion on the youngest component of the binary system;3.from the interaction of the stellar wind with the molec-ular material in the circumstellar envelope.The ﬁrst possibility seems the best one for originating fast (v s ∼50km s −1)dissociative J-type shocks,because the wind interaction would occur close to the stars where ve-locities are supposed to be high and the stellar ﬁeld strong to dissociate molecules.The second possibility has already been suggested by Quirrenbach &Zinnecker (1997)to ex-plain the near-infrared H 2extended emission.The third one is probably at work in any case,because it is needed to explain the strong emission from CO,H 2O,OH,as well as that from H 2(van den Ancker et al.1999).5.ConclusionsTo summarise our results,we list the main ﬁndings of this study:1.The far-infrared spectrum associated to the binary system of T Tau shows strong emission from CO,H 2O and OH molecules.2.Optically thin CO emission lines from high-J transi-tions are used to constrain the physical regimes of the gas:T ∼300-900K and n H 2∼105−6cm −3.The detec-tion of CO lines with J up of 24and 25seems to indicate that a warmer component is also needed.3.H 2O and OH emission is consistent with such condi-tions,however the higher excitation lines at the shorter wavelenghs are not well ﬁtted by these models,indicat-ing that higher temperature gas should also be present,in agreement with the CO emission.4.From the assumption that all the far-infrared molecu-lar emission observed originate from the same region a very compact size of 300-400AU of diameter is derived.5.The detection of [CII]158µm oﬀ-source at large dis-tances from T Tau shows that most of the ionised car-bon emission (∼80%)is from an extended region and not originated in the vicinity of T Tau.The intrinsic emission in the LWS beam centered on T Tau implies a ratio [OI]63µm/[CII]158µm of 115,much in excess of what is expected from photodissociation region mod-els.This emission is probably due to J-type shocks,。