Simple microscopic model of the magneto-electric effect in non-collinear magnets
T. A. Kaplan and S. D. Mahanti
Department for Quantum Sciences, Michigan State University, East Lansing, Michigan 48824
arXiv:cond-mat/0608227v1 [cond-mat.other] 10 Aug 2006
A 2-site 2-electron model with s- and p-states on each site, having constrained average site-spins Sa , Sb , with angle Θ between them, simpler than the previous closely-related model of Katsura et al (KNB), is considered. Intra-site Coulomb repulsion and inter-site spin-orbit coupling VSO are included. The ground state has an electric dipole moment π consistent with the result of KNB, π ∝ R × (Sa × Sb ) ≡ f , R connecting the two sites, and application to a spiral leads to ferroelectric polarization with direction f , also in agreement with the previous result. However, the present result shows the expected behavior π → 0 as VSO → 0, unlike the previous one.
where R connects the sites a and b, and Sa , Sb are the average spins at the sites. It is most closely related to that of [3], in that it considers the interaction of two magnetic sites with a center of symmetry (so there is no DMI). Also, the source of the spatial variation of the ordered spin density is due to outside effects of spin-spin exchange interactions, as in [3]. The hopping is direct–there is no oxygen, and no ionic displacements or orbital degeneracies. It involves inter -atomic spin-orbit coupling, a mechanism different from the model of [3]; it is obviously different from that of [1]. We add that these characteristics are more appropriate than the others for CoCr2 O4 , where there is no orbital degeneracy.[7, 9] A further motivation is a difficulty with the work of [3]. In the 3d transition metal ions, the spin-orbit coupling V SO is the smallest of the various energies, namely Coulomb interactions, transfer or hopping integrals, and (cubic) crystal field splitting. But in [3], V SO is taken as essentially infinite: it is diagonalized, along with the crystal field, before the hopping energies are considered. This leads to a doublet (Γ7 ) and a higher energy quartet (Γ8 ), and the quartet is dropped. This is probably the reason why π does not show the expected vanishing when V SO → 0. Our model does not have this difficulty. Our simple model has two atoms or ions, a and b, lying on the x-axis; each has an s-type orbital and 3 p-type orbitals lying an energy ∆ higher. Also, there are two electrons, 1 per site. Later we describe briefly the generalization to the case where each site has 3 t2g electrons, as for Cr3+ on an octahedral site, appropriate to the B-sites in XCr2 O4 , X=Co,Mn. For our simple model we first constrain the 1-electron basis set (including spin) to make the average spins < Sa >, < Sb > lie at particular angles in the x-y plane
PACS numbers: 75.80+q. 71.27.+a. 77.80.-e. 71.70Ej
INTRODUCTION
The magneto-electric (ME) effect, i.e. the production of an electric polarization (magnetic moment) by application of a magnetic (electric) field, has been known for a long time. Multiferroics, e.g. materials that show ferromagnetism and ferroelectricity coexisting, have also been known where spins and electric dipoles order at different temperatures. Quite recently a new class of multiferroics has been found, in which the magnetism and ferroelectricity are strongly coupled; e.g., they order at the same temperature. For this effect, however, the magnetic structure cannot be simple ferromagnetism or a collinear spin state; the (vector) magnetization density must show spatial variation in its direction as, e.g. for a spiral spin state. I refer to the introductory paragraphs of several recent papers for a more detailed history and list of references. [1, 2, 3, 4, 5] Until very recently, the effect has been found in antiferromagnets, e.g., simple spirals, with no net magnetic moment. In [5], however, the magnetic structure of the material studied, CoCr2 O4 , is approximately a ferrimagnetic spiral (there is a net moment). [6, 7, 8, 9] The work of Mostovoy [2] is a phenomenological theory (see also [10]), whereas microscopic models exhibiting the effect are presented in [1] and [3]. Both of the latter involve superexchange (where electron hopping between magnetic ions involves an intervening oxygen ion). In [3] the situation is considered where a nearest neighbor pair of magnetic ions has an inversion center at the mid-point, so that there is no Dzyaloshinsky-Moriya interaction (DMI) [11, 12]; the polarization comes from a distortion of electronic density without ionic or atomic displacements; also the t2g orbitals considered on each magnetic site are chosen to diagonalize the spin-orbit coupling (intra-atomic SO coupling), partially removing degeneracy of these orbitals. In contrast, the essential mechanism invoked in [1] depends on the existence of the DMI plus electron-lattice interactions and orbital degeneracy (Jahn-Teller effect), and the polarization results from ionic displacements.
物理学英文词汇
物理专业英语词汇(M)Favorite m center m 中心mach angle 马赫角mach cone 马赫锥mach number 马赫数mach wave 马赫波mach zehnder interferometer 马赫曾德耳干涉仪mach's principle 马赫原理machine language 机骑言machine oriented language 面向机颇语言macleod gage 麦克劳计macro crystal 粗晶macrography 宏观照相术macroinstability 宏观不稳定性macromolecule 高分子macron 宏观粒子macroparticle 宏观粒子macrophysics 宏观物理学macroscopic brownian motion 宏观布朗运动macroscopic particle 宏观粒子macroscopic quantization 宏观量子化macroscopic system 宏观系统macrostate 宏观态macrostructure 宏观结构macrosystem 宏观系统magdeburg hemispheres 马德堡球magellanic clouds 麦哲伦星系magellanic galaxy 麦哲伦星系magic eye 光党指示管magic lantern 幻灯magic number 幻数magic t t 形波导支路magma 岩浆magneli structure 马格涅利结构magnesium 镁magnet 磁铁magnetic 磁的magnetic amplifier 磁放大器magnetic analyzer 磁分析器magnetic anisotropy 磁蛤异性magnetic anomaly 磁异常magnetic axis 磁轴magnetic balance 磁力天平magnetic birefringence 磁双折射magnetic breakdown 磁哗magnetic bubble 磁泡magnetic bubble storage 磁泡存储器magnetic character figure 磁特正magnetic charge 磁荷magnetic chart 磁图magnetic circuit 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磁铃动力学magnetology 磁学magnetomechanical factor 磁力学因数magnetomechanics 磁力学magnetometer 磁强计magnetomotive force 磁通势magneton 磁子magnetooptics 磁光学magnetophotophoresis 磁光致泳动magnetoplasma 磁等离子体magnetoplasmadynamics 磁等离子体动力学magnetoplumbite 氧化铅铁淦氧磁体magnetopolaron 磁极化子magnetoreflection 磁反射magnetoresistance 磁阻效应magnetoresistor 磁致电阻器magnetosphere 磁层magnetostatic field 静磁场magnetostatics 静磁学magnetostriction 磁致伸缩magnetostriction oscillator 磁致伸缩振荡器magnetostrictive effect 磁致伸缩效应magnetothermal effect 磁致热效应magnetothermoelectric effect 磁致热电效应magnetron 磁控管magnetron vacuum gage 磁控管真空计magnification 放大率magnifier 放大镜magnifying glass 放大镜magnitude 量magnitude of the eclipse 食分magnon 磁振子magnus effect 马格努斯效应main quantum number 挚子数main sequence 烛main sequence stars 烛星main storage 宙储器major planets 大行星majorana force 马约喇纳力majorana neutrino 马约喇纳中微子majorana particle 马约喇纳粒子majorana spinor 马约喇纳旋量majority carrier 多数载劣majoron 马约喇纳量子maksutov telescope 马克苏托夫望远镜malleability 展性malter effect 马尔特效应malus law 马吕斯定律man made satellite 人造卫星mandelstam representation 曼德尔斯坦表象mandrin 细探针manganese 锰manganin 锰镍铜合金manifold 廖manipulator 机械手manometer 压力表manoscope 气体密度计manoscopy 气体密度测定manostat 稳压器mantle 地幔mantle convection 地幔对流mantle rayleigh wave 地幔瑞利波manual 手册many body force 多体力many body problem 多体问题many body system 多体系many wave approximation 多波近似mare 海margin 余量margin of error 误差范围margin of safety 安全因子marginal rays 边缘光线marine physics 海洋物理学mariner project 马里纳计划marisat system 海洋卫星系统mark 标记markoff chain 马尔柯夫链markoff process 马尔柯夫过程marriage of cable and satellites 电缆和人造卫星的联接mars 火星martensite 马氏体maser 微波激射器脉塞mass 质量mass absorption coefficient 质量吸收系数mass analysis 质量分析mass analyzer 质谱仪mass defect 质量筐mass effect 聚集效应mass energy conversion formula 质能换算公式mass energy equivalence principle 质能相当性原理mass energy relation 质能关系mass filter 滤质器mass flowmeter 质量量计mass formula 质量公式mass luminosity relation 质量发光度关系mass number 质量数mass renormalization 质量重正化mass separator 质量分离器mass shell 质壳mass spectrograph 质谱仪mass spectrometer 质谱仪mass spectroscopy 质谱法mass spectrum 质谱mass stopping power 质量阻止本领mass transfer 质量传递mass unit 质量单位massey criterion 梅涡据master equation 纸程master gyroscope 自由陀螺仪matching 匹配material 物质material point 质点material wave 物质波materials science 材料科学materials testing reactor 材料试验反应堆mathematical crystallography 数学晶体学mathematical expectation 数学期望值mathematical pendulum 单摆mathematical physics 数学物理mathematical programming 数学规划mathieu functions 马提厄函数matrix mechanics 矩阵力学matrix representation 矩阵表示matter 物质matter dominated universe 物质为诸宙matter wave 德布罗意波matthias rule 马赛厄斯定则matthiessen rule 马苇定则maupertuis' principle 莫佩尔秋原理maximum deviation 最大偏差maximum load 最大负载maximum lyapunov index 最大李亚普诺夫指数maximum permissible concentration 最大容许浓度maximum permissible dose 最大容许剂量maximum postulated accident 最大假设事故maximum speed 最大速度maximum stress 最大应力maximum temperature 最高温度maximum thermometer 最高温度表maximum velocity 最大速度maxwell 麦克斯韦maxwell boltzmann distribution 麦克斯韦玻耳兹曼分布maxwell boltzmann statistics 麦克斯韦玻耳兹曼统计maxwell bridge 麦克斯韦电桥maxwell demon 麦克斯韦妖maxwell field 麦克斯韦场maxwell relations 麦克斯韦关系maxwell velocity distribution 麦克斯韦的速度分布maxwell's distribution law 麦克斯韦分布律maxwell's equations 麦克斯韦方程maxwellian distribution 麦克斯韦分布maxwellmeter 磁通计mb 微巴mean acceleration 平均加速度mean deviation 平均偏差mean ergodic theorem 平均脯历经定理mean error 平均误差mean free path 平均自由程mean life 平均寿命mean lifetime 平均寿命mean solar day 平太阳日mean solar time 平太阳时mean square error 均方误差mean sun 平太阳mean value 平均值mean velocity 平均速度mean velosity 平场速度measure 测度measurement 测量measurement error 测量误差measuring 测量measuring apparatus 测量仪器measuring eyepiece 目镜测微计measuring instrument 测试仪器度量仪表measuring method 测量法measuring technique 测量技术mechanical energy 力学能mechanical equivalent of heat 热功当量mechanical filter 机械滤波器mechanical monochromator 机械单色器mechanical motion 力学运动mechanical system 力学系mechanical vibrations 机械振动mechanical world view of nature 机械的自然观mechanics 力学mechanism 机构mechanocaloric effect 机械热效应mechanochemistry 机械化学mechanoelectric conversion 机电变换mechanostriction 机致伸缩mechnical equivalent of light 光功当量medical electronics 医疗电子学medical physics 医用物理学medium 介质medium energy electron diffraction 中能电子衍射medium energy electron scattering spectroscopy 中能电子散射能谱学mega 兆mega electron volt 兆电子伏megacycle 兆周megawatt 兆瓦megger 高阻表megohm 兆欧meissner effect 迈斯纳效应meldometer 熔点测定计melt growth 熔体生长melting 熔化melting heat 熔化热melting point 熔点melting temperature 熔解温度membrane 膜memory 存储;记忆memory capacity 存储容量memory cell 存储单元memory effect 记忆效应memory register 存储寄存器mendeleev's periodic law 门捷列夫周期律mendelevium 钔meniscus 弯月面meniscus lens 弯月透镜mensa 山案座mercury 水星;水银mercury arc lamp 水银灯mercury arc rectifier 汞弧整流mercury barometer 水银气压表mercury cell 汞电池mercury diffusion pump 汞扩散泵mercury i chloride structure 氯化汞i型结构mercury relay 水银继电器mercury telemetry 水星遥测术mercury thermometer 水银温度表mercury vacuum gage 水银真空计mercury vapor lamp 水银灯meridian 子午线meridian passage 中天meridian transit 中天meridional ray 子午光线mesa transistor 台面型晶体管mesoatom 介子原子mesodynamics 介子动力学mesomolecule 介子分子mesomorphic state 介晶态meson 介子meson factory 介子工厂meson theory 介子理论meson theory of nuclear forces 核力的介子理论mesonic atom 介子原子mesonic molecule 介子分子mesopic vision 黄昏黎糜觉mesoscopic effect 介观效应mesosphere 中间层messier catalog 梅味星云星团表metacenter 定倾中心metal 金属metal film resistor 金属薄膜电阻器metal foil 金属箔metal insulator semiconductor light emitting diod 金属绝缘膜半导体发光二极管metal insulator transition 金属绝缘体跃迁metal nonmetal transition 金属非金属跃迁metal organic compound 有机金属化合物metal oxide semiconductor structure mos 结构metal vapor laser 金属蒸汽激光器metallic 金属的metallic binding 金属键metallic bond 金属键metallic crystal 金属晶体metallic element 金属元素metallic glass 金属玻璃metallic lustre 金属光泽metallic microcluster 金属微簇metallic reflection 金属反射metallic thin film 金属薄膜metallic valence 金属原子价metallized paper capacitor 镀金属纸介电容器metallography 金相学metallomicroscope 金相显微镜metallurgy 冶金学metamagnetism 亚磁性metastability 亚稳定性metastable atom 亚稳原子metastable equilibrium 亚稳平衡metastable level 亚稳能级metastable molecule 亚稳分子metastable nucleus 亚稳核metastable phase 亚稳相metastable state 亚稳状态meteor 燎meteor astronomy 燎天文学meteor camera 燎照相机meteor shower 燎雨meteor stream 燎群meteoric dust 燎尘meteoric iron 陨铁meteoric stone 石陨星meteorite 陨星meteorite crater 陨星坑meteoritic iron 陨铁meteoritics 陨石学meteorological acoustics 气象声学meteorological optics 气象光学meteorological radar 气象雷达meteorological satellite 气象卫星meteorological thermodynamics 气象热力学meteorology 气象学meter 米meter convention 米条约meter standard 米原器meter wave 米波metering 计量metglass 金属玻璃method 方法method of approximation 近似法method of crystal projection 晶体投影法method of difference 差分法method of images 镜象法method of iteration 迭代法method of least squares 最小二乘法method of measurement 测量法method of molecular orbitals 分子轨迹法method of perturbation 微扰法method of steepest descent 最陡下降法method of successive approximation 逐次逼近法method of undetermined coefficients 待定系数法metonic cycle 太阴周metre 米metre wave 米波metric 度规metric space 度量空间metric system 米制metric tensor 度规张量metrology 计量学metronome 节拍器mhd arc mpd 弧光mho 闻子mica 云母micelle 胶体微粒michel parameter 米歇尔参数michelson interferometer 迈克耳逊干涉仪michelson morley experiment 迈克耳逊莫雷实验michelson stellar interferometer 迈克耳逊恒星干涉计micro 微microaccelerometer 微加速计microaerotonometer 微量气体张力计microampere 微安microanalysis 微量化字分析microbalance 微量天平microbar 微巴microcanonical ensemble 微正则系综microchemical analysis 微量化字分析microchemistry 微量化学microcomputer 微型计算机microcrystal 微晶microcrystalline 微晶的microcrystallography 微观结晶学microengineering 微工程学microfarad 微法microfield 微场microfilm 缩微胶片micrography 显微照相术microinstability 微不稳定性microlaser 微型激光器microlock 卫星遥测系统micromagnetics 微磁学micromanometer 微压力计micrometer 测微计micrometer microscope 测微显微镜micrometron 自动显微镜micromicrocurie 微微居里micromicrofarad 微微法micron 微米microoscillograph 显微示波仪microparticle 微观粒子microphone 传声器microphotograph 显微镜照片microphotometer 测微光度计microphysics 微观物理学microplasma 微等粒子体microprobe 微探针microprogram 微程序microprojector 显微投影仪micropyrometry 微测高温术microscope 显微镜microscopic brownian motion 微观布朗运动microscopic particle 微观粒子microscopic state 微观状态microscopic system 微观系统microscopium 显微镜座microsecond 微秒microseismics 微地震学microseismograph 微震记录仪microspectrofluorimeter 显微荧光光谱仪microspectrograph 显微光谱仪microspectrophotometry 显微分光光度学microspectroscope 显微分光镜microspectroscopy 显微光谱学microstate 微观状态microstructure 显微结构microsystem 微观系统microtelescope 显微望远镜microthermometer 微温度计microthermometry 显微温度学microtron 电子回旋加速器microwave 微波microwave circuit 微波电路microwave diode 微波二极管microwave method 微波法microwave resonator 微波谐振器microwave spectroscopy 微波谱学microwave spectrum 微波频谱microwave transistor 微波晶体管microwave tube 微波电子管microwave ultrasound 微波超声microwave weapon 微波武器mie scattering 米散射migdal approximation 米格达尔近似migration length 迁移长度mil 密耳mile 英里milky way 银河miller index 密勒指数miller's notation 密勒记号milli 毫milliampere 毫安millibar 毫巴millimeter 毫米millimeter wave 毫米波millimetre 毫米million electorn volt 兆电子伏millisecond 毫秒millivolt 毫伏millivoltmeter 毫状计mimosa seismic foreteller 含羞草地震预报器miniature tube 微型管miniature valve 微型管minicomputer 小型计算机miniinfraredtracer 微型红外示踪器minilaser 微型激光器minimal interaction 最小耦合相互酌minimax principle 极大极小原理minimum b field 最小磁场minimum deviation 最小偏向minimum entropy production 最小熵产生minimum thermometer 最低温度表minkowski space time 闵科夫斯基时空minor planet 小行星minority carrier 少数载劣minus 减minus sign 减号minute 分mira stars 刍藁变星mira type variables 刍藁变星mirage 蜃景mirror field 磁镜场mirror nuclei 镜象核mirror reflection 镜反射mirror surface 镜面mirror telescope 反射望远镜misfit dislocation 错配位错missile 导弹missing line 丢失线missing mass 暗物质mistake 错误mixed crystal 混合晶体mixed state 混合态mixer diode 基模mixer tube 混频管mixing length 混合长度mixing ratio 混合比mixture 混合物mks system of units mks 单位制;mks单位制mksa system of units mksa 单位制mobile laser tracking station 移动激光追踪站mobility 迁移率mobility of ions 离子迁移率mode 模mode coupling 模耦合mode locked laser 锁模激光器mode locking 锁模mode of oscillation 振动型mode of vibration 振动型mode pulling 波模牵引model 模型model of nucleus 核模型model of the galaxy 银河系模型moderated neutron 慢化中子moderation 减速moderation of neutrons 中子减速moderator 减速剂modern biology 现代生物学modern physics 现代物理学modification 变形modular invariance 模数不变性modulated structure 灯结构modulation 灯modulation method 灯法modulation spectroscopy 灯光谱学modulation transfer function 灯传递函数modulator type vacuum gage 灯仆真空计module 模件modulus 模数modulus of elasticity 弹性模数modulus of rigidity 剪切殚性模量moffatt's vortex 莫法特涡旋mohoroviris discontinuity 莫霍洛维奇不连续性mohs hardness 莫氏硬度moist labile energy 潮湿不稳能moisture examining instrument 水气检查仪mol 克分子molar fraction 克分子分率molar heat 分子热molar polarization 克分子极化molar refraction 分子折射molar susceptibility 克分子磁化率molar volume 克分子体积molding 制模mole 克分子mole fraction 克分子分率molectronics 分子电子学molecular absorption coefficient 分子吸收系数molecular acoustics 分子声学molecular astronomy 分子天文学molecular beam 分子束molecular beam epitaxy 分子束外延molecular beam magnetic resonance 分子束磁共振molecular beam maser 分子束微波激射器molecular beam scattering 分子束散射molecular beam spectroscopy 分子束光谱学molecular biology 分子生物学molecular bond 分子键molecular chaos 分子混沌态molecular clock 分子钟molecular cloud 分子云molecular compound 分子化合物molecular conductivity 分子导电率molecular crystal 分子晶体molecular diffusion 分子扩散molecular dynamics 分子动力学molecular electronics 分子电子学molecular field 分子场molecular field approximation 分子场近似molecular flow 分子流molecular force 分子力molecular force field 分子力场molecular gas laser 分子气体激光器molecular heat 分子热molecular image 分子图象molecular integral 分子积分molecular inversion 分子倒转molecular ion 分子离子molecular kinetic theory 分子运动论molecular lattice 分子晶格molecular magnet 分子磁铁molecular mass 分子质量molecular motion 分子运动molecular orbital 分子轨函数molecular physics 分子物理学molecular polarizability 分子极化度molecular polarization 分子极化molecular pump 分子泵molecular radius 分子半径molecular rays 分子束molecular reaction 分子反应molecular refraction 分子折射molecular rotation 分子转动molecular scattering 分子散射molecular science 分子科学molecular sieve 分子筛molecular structure 分子结构molecular structure theory 分子结构论molecular viscosity 分子粘性molecular volume 克分子体积molecular weight 分子量molecule 分子moletron 分子加速器molten high polymer 熔融高聚物molybdenum 钼moment 矩moment of couple 力偶矩moment of force 力矩moment of impulse 冲量矩moment of inertia 转动惯量moment of momentum 角动量momentum 动量momentum space 动量空间momentum transfer 动量转移momentum transfer cross section 动量转移截面momentum transfer theory 动量转移理论monaural audition 单耳听力monitor 监测器监视器monoatomic gas 单原子气体monoatomic layer 单原子层monoceros 座monochord 弦音计monochromat 单色透镜monochromatic aberration 单色象差monochromatic light 单色光monochromatic radiation 单色辐射monochromatic rays 单色射线monochromaticity 单色性monochromatization of neutron 中子的单色化monochromatization of x rays x 射线单色化monochromator 单色器单色光镜monoclinic system 单斜晶系monocrystal 单晶monocular 单筒望远镜monodispersive system 单分散系monolithic circuit 单片电路monomer 单体monomode laser 单模激光器monomolecular film 单分子膜monopole 单极monopole moment 单极子矩monopole transition 单极跃迁monostable multivibrator 单稳多谐振荡器monotectic 偏晶体monte carlo method 蒙特卡罗法month 月moon 月球moon power station 月球发电站moon's age 月龄morning star 晨星morphophysics 形态物理学morse potential curve 莫尔斯势能曲线mos diode mos 二极管mos field effect transistor mos 金属氧化物半导体场效应晶体管mos integrated circuit mos 集成电路mos structure mos 结构mosaic crystal 嵌镶晶体mosaic structure 嵌镶结构moseley's law 莫塞莱定律mosfet mos 金属氧化物半导体场效应晶体管motion 运动motion equation 运动方程motor 电动机mott insulator 莫脱绝缘体mott scattering 莫脱散射mott transition 莫脱跃迁mottelson valatin effect 莫特尔逊瓦拉廷效应movement of the pole 极运动movement stability 运动的稳定性moving cluster 移动星团moving coil galvanometer 动圈检疗moving iron vane instrument 动叶式仪表moving magnet galvanometer 动磁型电疗moving magnet instrument 动磁式仪表moving medium acoustics 运动介质声学moving striation 活动条纹mpd arc mpd 弧光mtller scattering 摩利尔散射mts system of units mts单位制mu factor 放大系数multi color photometry 多色测光multi crystal x ray spectrometer 多晶x 射线光谱仪multi function observer 多功能观测器multichannel interferometric spectrometer 多道干涉光谱仪multichannel pulse height analyzer 多道脉冲高度分析器multienzymatic reaction 多酶反应multifilament composite wire 多丝结构复合线multigroup model 多群模型multilayer film 多层胶片multilayer mirror 多层反射镜multimode laser 多模激光器multimolecular layer 多分子层multiparticle correlation 多粒子关联multiparticle production 多粒子产生multiphase flow 多相流multiphoton absorption 多光子吸收multiphoton dissociation 多光子离解multiphoton process 多光子过程multiphoton transition 多光子跃迁multiple beam interference 多光束干涉multiple beam interferometry 多光束干涉测量法multiple collision 多次碰撞multiple correlation 多重相关multiple coulomb scattering 多次库仑散射multiple electrode tube 多栅管multiple electrode valve 多栅管multiple excitation 多次激发multiple galaxy 多重星系multiple ionization 多次电离multiple mirror telescope 多镜望远镜multiple periodic motion 多周期运动multiple process 多重过程multiple production 多重产生multiple reflection 多次反射multiple refraction 多次折射multiple scattering 多次散射multiple star 聚星multiple structure 多重结构multiplet 多重线multiplet term 多重项multiplication 增殖multiplication factor 倍增系数multiplicity 多重性multiplier 倍增器multiply connected region 多连通域multiply periodic motion 多重周期运动multiply twinned particle 多重孪晶粒子multiplying factor 倍率multipole 多极multipole expansion 多极展开multipole moment 多极矩multipole radiation 多极辐射multipurpose minicamera 多功能缩微照相机multipurpose reactor 多用堆multislit spectrometry 多狭缝能谱测定法multispectral photography 多谱照像术multispectral satellite data 多谱卫星数据multitarget tracking 多目标跟踪multivariate analysis 多变量分析multivibrator 多谐振荡器multiwire chamber 多丝室multiwire counter 多丝计数管mumeson 介子muon 介子muon beam 子束muon capture 子俘获muon catalyzed fusion 子催化聚变muon neutrino 子中微子muon number 子数muon spin rotation 子自旋转动muonic atom 原子muonic catalysis 子催化muonium 子偶素murchison meteorite 默基森陨星musca 苍蝇座musical acoustics 音乐声学musical scale 音阶musical sound 乐音muspace 空间mutarotation 变旋mutation 突变mutual conductance 互导mutual inductance 互感mutual induction 互感应mutual neutralization 互中性化myopia 近视myria 万myriad 一万myriads 无数myriameter 万米myriametric wave 超长波。
Quantum Mechanics
Quantum MechanicsQuantum mechanics is a branch of physics that deals with the behavior of matter and energy at a microscopic level. It is a fundamental theory that explains how the universe works at its most basic level. Quantum mechanics is a complex and fascinating field that has revolutionized our understanding of the universe. In this essay, I will explore the basics of quantum mechanics, its implications, and the challenges it presents.At the heart of quantum mechanics is the concept of the wave-particle duality. This means that particles, such as electrons and photons, can behave as both waves and particles. This is a fundamental departure from classical physics, which assumes that particles are always particles and waves are always waves. The wave-particle duality is a key aspect of quantum mechanics and is essential to understanding its many applications.One of the most famous applications of quantum mechanics is in the field of quantum computing. Quantum computers use the properties of quantum mechanics to perform calculations that are impossible for classical computers. This is because quantum computers can perform multiple calculations simultaneously, whereas classical computers can only perform one calculation at a time. Quantum computers have the potential to revolutionize fields such as cryptography, drug discovery, and artificial intelligence.Another important aspect of quantum mechanics is quantum entanglement. This is a phenomenon where two particles become entangled and share a quantum state. When this happens, any change to one particle will instantly affect the other particle, no matter how far apart they are. This has important implications for the field of quantum communication, where information can be transmitted using entangled particles. Quantum entanglement also has implications for the nature of reality, as it challenges our classical understanding of causality and locality.Despite its many applications, quantum mechanics presents many challenges. One of the biggest challenges is the measurement problem. In quantum mechanics, particles exist in a state of superposition, where they can exist in multiple states simultaneously. However, when a measurement is taken, the particle collapses into a single state. This presents a paradox, as it is unclear whatcauses the collapse of the wave function. This has led to many interpretations of quantum mechanics, such as the Copenhagen interpretation, the many-worlds interpretation, and the pilot wave theory.Another challenge presented by quantum mechanics is the problem of decoherence. Decoherence is the process by which a quantum system interacts with its environment, causing it to lose its quantum properties. This makes it difficult to maintain a quantum state for any length of time, which is a major obstacle for the development of practical quantum technologies.In conclusion, quantum mechanics is a fascinating and complex field that has revolutionized our understanding of the universe. It is a fundamental theory that has many applications, from quantum computing to quantum communication. However,it also presents many challenges, such as the measurement problem and the problem of decoherence. Despite these challenges, quantum mechanics is a field that is constantly evolving, and it will continue to shape our understanding of the universe for many years to come.。
显微镜的英语作文
显微镜的英语作文Microscopes have been a cornerstone of scientific discovery since their invention. They have allowed us to explore the microscopic world that is invisible to the naked eye. In this essay, we will delve into the history of microscopy, its various types, and the impact it has had on our understanding of the natural world.The first microscopes were simple, with limited magnification power. However, they laid the groundwork for the sophisticated instruments we have today. As technology advanced, so did the complexity and magnificationcapabilities of microscopes. The electron microscope, for example, can magnify objects up to two million times their original size, revealing atomic and molecular structures.There are several types of microscopes, each serving a specific purpose. The compound light microscope is the most common and uses visible light to magnify samples. The scanning electron microscope (SEM) uses electron beams to create detailed images of surfaces, while the transmission electron microscope (TEM) is used to study thin samples at an atomic level.Microscopes have revolutionized fields such as biology, medicine, and materials science. In biology, they have enabled us to study cells and microorganisms, leading to breakthroughs in understanding life processes. In medicine,they have been instrumental in the diagnosis of diseases by allowing doctors to observe pathogens and cellular changes. Materials science has also benefited from microscopy, as it allows for the examination of material structures and defects at a microscopic level.Moreover, the use of microscopes extends beyond the laboratory. They are used in forensic science to analyze evidence, in environmental science to study microorganisms and their impact on ecosystems, and in education to teach students about the unseen world.In conclusion, microscopes are not just scientific tools; they are windows into a world that is as complex and diverse as the macroscopic world we inhabit. They have expanded our knowledge and continue to be essential in the quest for understanding the intricate details of life and matter. As technology progresses, we can expect microscopes to become even more powerful, unveiling even more secrets of the microscopic universe.。
蒙特卡洛方法
(1915 - 1999)
More sophisticated algorithms: Different types of moves: (i) a particle is displaced, (ii) a particle is destroyed (no record kept), and (iii) a particle is created at a random position. Micorscopic reversibility by making the creation and destruction probabilities equal. Problems with high rejection rates (unfavorable overlaps when particle is created).
Grand Canonical Monte Carlo IV Movie
Kinetic Monte Carlo
Allows to simulate time evolution. However, not at the molecular level but by introducing reaction rates (which have to be known from elsewhere, e.g., from transition state theory). - At each step, system can jump from state A into one of the ending states Bi. survival probability: psurvival(t) = exp (-ktot t), ktot = ΣkABi integrated probability of escape between 0 and t: 1 – psurvival(t) - Repeated many times – Markovian process, i.e., system looses memory before doing the next step.
卡尔·泽伊斯 SteREO Discovery.V20 立体显微镜说明书
M i c r o s c o p y f r o m C a r l Z e i s sSteREO Discovery.V20The New SpectrumZoom Factor 20 in Stereomicroscopy –More Flexibility Between Overview andDetail MagnificationSFact Innovation:Never Before hasthe MagnificationSpectrum beenLarger.There’s a new performance standard in the demandingworld of stereomicroscopy: Zoom Factor 20. The factorfor the largest spectrum between overview and detailmagnification. The microscope: SteREO Discovery.V20.A Carl Zeiss design. And a research instrument withwhich the pioneer of the CMO principle (C ommon M ainO bjective) has once again broken new ground for thefuture of stereomicroscopy after the telescope principle.The development of the SteREO Discovery.V20 hasexceeded the limits of conventional modes of action.Founded on a new technological base and integratedinto the SteREO* generation series from Carl Zeiss,SteREO Discovery.V20 is highly impressive and boastsa superior performance profile. For maximum precisionand considerably more freedom in biology, medical andindustrial labs. The new features:• planapochromatic corrected microscope bodieswith a zoom range of 20:1• high end magnification of up to 345x(with eyepiece 10x)• maximum resolution of 1000LP/mm(with objective PlanApo S 2.3x)• excellent 3D-effect up to the highestmagnification• comfortable, securely reproducible operationaland control concept with SyCoP• seamless integration into the modular systemof the SteREO Discovery generation* SteREO – Stereomicroscopy Redefined in Ergonomics and Optics2teREO Discovery.V2034SyCoP 1.2.3.3.Extraordinarily large working area:the stand design with decentralized profile column S.The Performance Factor:Superiority Can be DocumentedAt the borders of technical possibilities details become a critical factor. Better optics is responsible for a visible improvement in image information. The easier operation concept delivers faster results. Fac-tors which Carl Zeiss places the utmost importance on in development and consistently optimizes until the peak of performance is reached. The results create new benchmarks. At any place where living objects or material samples are observed, manipulated or documented in detail, three-dimensionally and with high resolution or high contrast.1A in 3D: Spatial impressionWith SteREO Discovery.V20, higher magnifications can also be realized with smaller lenses thanks to the large zoom range of the microscope body. The smaller stereo angles associated improve the 3D impression of the microscopic image. The result:you remain more relaxed during observation and notice even the smallest details.Secure the highest magnifications: StabilityHigh image resolution and end magnification place new demands on the stability of the stand system of this stereomicroscope. All relevant components were designed and built according to the most modern methods. The stands feature a significantly higher rigidity and is considerably less susceptible to vibrations than previous systems. The motor focusing makes fine focusing in intervals of 350 nm in a range of 340 mm for loads of up to 17 kg possible.1.With SyCoP,even the most complex stereomicroscopic operation procedures can be handled comfortably.Without letting the sample out of your sight.With one hand,reliable and flawless.2.The new SteREO Discovery.V12 zoom body is parfocally adjusted.For pin sharp pictures in the complete magnification range.5Increase free space:Zoom factor 20:1The largest range from overview to detail –SteREO Discovery.V20 has brought a new zoom range into the research laboratory. And what’s more: even the basic configuration of this top ste-reomicroscope offers an end magnification of 150x.Equipped with the nosepiece S. cod as well asthe objectives PlanApo S 0.63x, PlanApo 1x and PlanApo S 2.3x, SteREO Discovery.V20 covers a magnification range from 4.7 to 345x. That is a factor of 73! With only one turn of the nosepiece.Decide economically:The SteREO Discovery upgrade conceptSteREO Discovery offers a wide spectrum of com-patible modules and accessory components. No matter what instrument type you choose, you have the freedom to upgrade your system according to your needs at any time. Up to the highest-capacity Imaging System that stereomicroscopy has to offer currently.Sophisticated and universally compatible:the wide accessory range fits for every instrument type of the SteREO Discovery generation.Intelligent operation: SyCoPSyCoP stands for S ystem C ontrol P anel and for a considerable gain in time, overview capability and flexibility in the operation of increasingly complex operation procedures. Designed especially for the demands of stereomicroscopy, the novel operation concept combines joystick, keys and touch screen in the handy design of a computer mouse. With SyCoP ,almost all important microscope functions can be controlled virtually location-independent. Fast, pre-cise and reproducible. Without removing your eye from the eyepiece ocular. Your attention stays on the object. In addition, SyCoP provides current data about the total magnification, object field, resolution and depth of focus of your microscope setting.SyCoP is an option for the future. New functions and further accessories are integrated through the open CAN-Bus concept.SteREO Discovery.The Technology Factor:Exceeding the LimitsAt the limits:The conventional technologyThe centerpiece of a CMO stereomicroscope is the pancrat (microscope or zoom body). During zoom-ing, lenses are moved and must be brought into a certain position in relation to other securely in-stalled lenses with extraordinary precision. Until now a mechanical curve – a simple metal piece milled with great care – determined largely parts the exactness of the traverse path of these lenses and thereby the overall microscope quality. The precision required for new stereomicroscope generations can no longer be fulfilled in this way. The solution:The new active principleOn the SteREO Discovery.V20, this mechanical curve has been replaced by a virtual one. The movable lenses are moved with a stepping motor and posi-tioned exactly with a processor. The microscopic images then stay considerably sharper. That has some definite advantages for your research applications:• 3D images can be viewed in the stereomi-croscope in a noticeably more relaxed way The partial images which are produced for our eyes are much sharper and better coordinated. The effort of the brain to create a 3D imageis less.• Sharper images producecontrast improvementsParticularly decisive when the stereomicroscopeis used in high and the highest magnifications. Microscopy pushed to the limits of useful magnification.• Higher magnifications with alarger zoom rangeUntil recently a zoom with a factor of 16 butnot higher was considered technically possible but this limit can now be exceeded considerably with this new technology. And it’s affordable.Carl Zeiss has created a new milestone in stereomi-croscopy with the SteREO Discovery.V20. Over 30 invention disclosures and patent applications are pro-viding that this technological advantage is preserved.Better 3D images, higher resolution, larger zoomranges – technologically, the conventional stereo-microscope has reached its limits. Each lens, eachmechanical detail exhibits tolerances – regardless ofthe precision of the production. The higher thedemands on resolution and magnification become,the less acceptable are these tolerances.Fast,flexible and effective: the final assembly of the stereomicroscopeSteREO Discovery in the clean rooms of Carl Zeiss Micro scopy GmbHin Jena.It is customized as “individual item chain production according tothe Wertstrom design criteria”.671.2.3.4.5.6.V20Zoom position of pancratD e f o c u s p o s i t i o n i n µmDepth of field curve, with in these parameters the picture is in focusTypical defocus curve of one channel with classical adjustment (pancrat with mechanical zoom curve)T ypical defocus curve of one channel of the SteREO Discovery.V20(pancrat with virtual electronically derived curve)1.Before the assembly begins each lens is exactly calibrated against a “0-lens type”.This lens value is digitally saved in a data pool – the basis on which computer-calculated combinations are established.By doing this,an optimally coordinated lens family is developed for every individual microscope2.Rotating reflexes of a lens.As soon as it is in the circle…3....a moveable micro clapper of the computer-controlled glue leveling machine autonomously undertakes the fine alignment.4.After being moved into place,the lenses are immediately fixed.Precision tools automatically lay high-precision,uninterrupted glue beads through a strong cannula 0.5 mm wide.5.Hardening of the glue beads under UV-radiation.6.In the pancrat adjusting device,the precise procedures of all moveable optical elements are programmed.To do this,around 7000 supporting points are analyzed via computer.In doing so,each stereomicroscope obtains its own correc-tion – its own individual zoom control curve.Illustration of the defocus curve of a classical mechanical pancrat in comparison to a motorized one (SteREO Discovery.V20).It is clear that the motorized pan-crat differs from the 0 line about half less than the mechanical one.That means:SteREO Discovery.V20 with motorized pancrat delivers twice as sharp images.8S1. 2. 4.3.1. Tubes Today ergonomics is a basic demand on microscopy.The user’s posture should remain relaxed even over long periods of work. An important factor for this are the observation tubes. The eyepiece sockets are swingable and adjustable in two levels. With the ergotube the angle of vision can be individually adjusted between 5 and 45 degrees.2. ObjectivesObjectives largely determine the image quality –and they are a relevant economic factor. The selec-tion of objectives for the SteREO Discovery.V20receives special attention for a reason. The spectrumranges from the cost-effective objectives of the Achromat series to the high-capacity Plan-Achromat objectives to the Plan-Apochromat series, which meets the highest requirements.3. StagesDesigned to move your objects gently and jolt-free during observation – a wide spectrum of different stages is available for the SteREO Discovery.V20.According to your needs, choose from sliding,rotating, mechanical or ball-and-socket stages.The motorized mechanical stage offers an addi-tional advantage in precision when adjusting and controlling objects: precisely accurate, fast and reproducible.4. FluorescencePentaFluar S is the retrofittable intermediate tube with a coaxial fluorescence mechanism which con-verts your SteREO Discovery.V20 into a high-capacity fluorescence system. The filter turret holds up to five filter modules and there are also many possibilities regarding illumination. Besides the well-established HBO lamps, X-Cite 120 with a liquid lightguide is recommended.The Flexibility Factor:the Upgrade Possiblities are EndlessThe modular construction of the SteREO Discovery.V20is typical for main lens stereomicroscopes. The multi-tude of accessory components which you can have installed on the high-capacity stereomicroscope in order to create an effective observation and docu-mentation system is correspondingly wide . The flexi-bility is unusual: completely integrated into the Carl Zeiss system world and equipped with intelligent interfaces, each component can be installed for every instrument type in the SteREO Discovery range.teREO Discovery.V205. 6.8.5. CamerasThe demands on the documentation of microscopic images in research are as different as the projects themselves. The spectrum of digital microscope cameras for the innovative high-performance system SteREO Discovery.V20 is correspondinglydiverse. Starting with digital consumer cameras through to professional cameras of the microscope camera family AxioCam, Carl Zeiss offers you a suit-able price and performance class for every demand.6. IlluminationThe quality of illumination essentially determines the quality of the results – in particular with stereo-microscopic contrasts. With an elaborate system of interfaces and adapters, SteREO Discovery.V20 can be equipped with modern fiber optic LED-compo-nents. Optimal for the illumination and contrasting of various objects.7. OperationCompletely motorized, SteREO Discovery.V20 offers reproducibility and considerable simplifications for your experiment procedures. In particular for con-trolling object details as well as for setting illumina-tion and contrasts. In addition, the innovative control system is now available. Designed to be user-friendly and securely operable. This is the foundation of thefact that the control of the current highest-capacity stereomicroscopy research device practically runsitself.8. Microscope SoftwareAxioVision is the superior software for microscopecontrol, image acquisition, image processing,image administration and archiving. With a univer-sal modular design and upgradeable according toyour needs from the basic version to the mostdemanding special configuration. The microscopesoftware from Carl Zeiss is completely integrated tothe current highest-capacity analysis platform andholds a top position worldwide on account of itssimple operation principle and its high productivity.9101.2.3.STrue to reality, completely shift-free 3D imaging of the researched specimen are the demands of contemporary stereomicroscopy. From a complete overview down to the smallest detail like organs,tissues and neurons. Now, Carl Zeiss raises the bar even higher.SteREO Discovery.V20 with its zoom of 20x doesn’t just deliver a large magnification range, it also shines with a brilliant image quality in the research of living specimen and other objects of Life Science. The con-sequent minimization of stray light of all tubes, the zoom body and the objectives as well as the indi-vidually tailored zoom curve, allow for a rich contrast in the images over the entire zoom range – from the overview up to the highest magnification. The large base and the grand front lens add to the unique 3D effect.Therefore the SteREO Discovery.V20 ensures an image quality that you can count on in research facilities and laboratories of biology and medicine. It is also ideal to observe and research model organ-isms of developmental biology.Practical Life Sciences:High Magnifications,Excellent Depth Perception1.Mouse embryo,stained,transmitted-light brightfield,objective PlanApo S 0.63x,magnification 4.7x*2.Mouse embryo,stained,transmitted-light brightfield,objective PlanApo S 0.63x,magnification 94x*3.Diatome,transmitted-light darkfield,objective PlanApo S 2.3x,magnification 345x*111.2.teREO Discovery.V20The demands for high-end stereomicroscopes rise with the perception of smaller details. On one hand there is the need for fast orientation of where you are in the specimen and that requires a large overview. On the other hand there is the need for observing and documenting the smallest detail in a rapid switch from the overview image – ideally without re-focussing.The SteREO Discovery.V20 with a zoom of 20x gives you a vast advantage in your lab. It is the only stereomicroscope that allows a fast switch from overview to detail image. Here the motorised zoom delivers a precise and free to choose zoom position.And it only differs less than 1%. That means a reproducibility of more than 99%! This is the pre-cision of an ideal research instrument with its always correctly scaled images to measure and document tasks in micromechanics and quality control. And it is a safe investment into a new dimension of achievement.Practical Materials:99% Reproducibility,100% Investment Security1.Semiconductor,reflected-light darkfield,objective PlanApo S 1x,magnification 7.5x*2.Semiconductor,reflected-light darkfield,objective PlanApo S 1x,magnification 150x*3.Semiconductor,reflected-light darkfield,objective PlanApo S 1x,magnification 20x*,Extended Depth of Focus* Total magnification through eyepiecesObjectivesEyepiecesSteREO Discovery.V20:The Technical DataCarl Zeiss Micro scopy GmbH 07745 Jena, Germany ********************www.zeiss.de/stereo-discoveryP r i n t e d o n e n v i r o n m e n t a l l y -f r i e n d l y p a p e r , b l e a c h e d w i t h o u t t h e u s e o f c h l o r i n e .S u b j e c t t o c h a n g e .46-0128 e 05.2007。
定语从句的翻译ppt课件
当从句具有转折意义时，除重复关系代词所 代的名词之外，还须加连词“而”、 “但”、“可是”等。
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Matter is composed of molecules that are composed of atoms.
物质是由分子构成的，而分子又是由原子构 成的。
A metal will bear beating with a hammer, which a stone will not.
液压仿形适合于宇航工业，但这种工业当时 在欧洲尚处于发展阶段。
24
The additional ozone may absorb more than the usual amount of the sun's heat, which in turn may effect our weather.
增加的臭氧吸收比正常量更多的太阳的热量，从 而影响到我们的天气。
所有生命体都由极小的细胞构成，借助显微镜可 以看到其形状。
The control unit is an important part of the computer, which can cause the machine to operate according to man’s wishes.
控制器是计算机的重要部分，它能使计算机按人 们的意愿进行操作。
Strength, hardness and plasticity of metals are the properties that make them so useful for industry.
6
So the preparation of a pure culture involves the isolation of a given microorganism from a mixed natural microbial population
Importance of quantum interference in molecular-scale devices
Importance of quantum interferencein molecular-scale devicesKamil Walczak 1Institute of Physics, Adam Mickiewicz UniversityUmultowska 85, 61-614 Poznań, PolandElectron transport is theoretically investigated in a molecular device made of anthracene molecule attached to the electrodes by thiol end groups in two different configurations (para and meta, respectively). Molecular system is described by a simple Hückel-like model (with non-orthogonal basis set of atomic orbitals), while the coupling to the electrodes is treated through the use of Newns-Anderson chemisorption theory (constant density of states within energy bandwidth). Transport characteristics (current-voltage and conductance-voltage) are calculated from the transmission function in the standard Landauer formulation. The essential question of quantum interference is discussed in detail. The results have shown a striking variation of transport properties of the device depending on the character of molecular binding to the electrodes.Key words: molecular device, quantum interference, electronic transport, molecular electronicsPACS numbers: 85.65.+h , 73.23.-bI. IntroductionMolecular junctions are promising candidates as future electronic devices because of their small size and self-assembly features. Such junctions are usually composed of two metallic electrodes (source and drain) joined by individual molecule (bridge). The charge is transferred under the bias voltage and current-voltage (I-V) characteristics are measured experimentally [1]. In general, transport properties of such structures are dominated by some effects of quantum origin, such as: tunneling, quantization of molecular energy levels and discreteness of electron charge and spin. However, recently it was pointed out that also quantum interference effects can lead to substantial variation in the conductance of molecule-scale devices [2-9].The main purpose of this work is to show some theoretical aspects of interference phenomena in anthracene molecule connecting two identical electrodes by thiol (–SH) end groups (see fig.1). These end groups (or more precisely sulfur terminal atoms, since hydrogen atom seems to be lost in the chemisorption process) ensure readily attachment to metal surfaces [10]. It is shown that the molecule acts not only as a scattering impurity between two reservoirs of electrons (electrodes), but simultaneously as an “electronic interferometer”. Interference itself reveals the wave nature of the electrons passing from the source to drain through the molecule. Here the variation of interference conditions is achieved by changing the connection between anthracene molecule and electrodes.Fig.1 A schematic model of analyzed samples.II. Theoretical treatmentMolecular device is defined as anthracene molecule joined to two metallic surfaces with the help of thiol end groups in two different configurations – para (A) and meta (B), respectively. In both cases we have different interference conditions and so we expect to observe changes in transport characteristics. Problem of electronic conduction between two continuum reservoirs of states via a molecular bridge with discrete energy levels can be solved within transfer matrix technique of scattering theory [11,12]. The current flowing through the device is obtained from the transmission function T through the integration procedure [12]: []dE )E (f )E (f )E (T h e 2)V (I D S m m ---=ò+¥¥-, (1)where: f denotes Fermi distribution function for room temperature (293 K) with chemical potentials 2/eV E F D /S ±=m referred to the source and drain, respectively. In this type of non-self-consistent calculations, one must postulate voltage distribution along the molecular bridge. For the sake of simplicity we assume that voltage drop is limited to the electrodes only [13], shifting their Fermi level located in the middle of the HOMO-LUMO gap [14]. However, other choices of the voltage distribution have only a small effect on our final results and general conclusions. The differential conductance is then calculated as the derivative of the current with respect to the voltage [15]:[])(T )(T G G D S 021m m +=, (2) where 5.77h /e 2G 20»= [μS] is the quantum of conductance.Formula for the transmission probability can be expressed in the convenient matrix form[12]:[]+++--=G )(G )(tr )E (T D D S S S S S S , (3)where D /S S and are self-energy terms of the source/drain electrode and the Green ’s function of the molecule is expressed as follows:1D S ]H ES [G ----=S S . (4)Here S denotes overlapping matrix (where the overlap between the nearest-neighbor sites is assumed to be equal to 0.25). Since only delocalized π-electrons dictate the transport properties of organic molecules, the electronic structure of the molecule is described by a simple H ückel Hamiltonian H with one π-orbital per site (atom) [16], where overlapping is explicitly included (using non-orthogonal basis set of atomic orbitals). Throughout this work we take the standard energy parameters for organic conjugated systems: on-site energy is 6.6-=a eV and nearest-neighbor hopping integral is 7.2-=b eV. In the H ückel π-bond picture, all carbon and sulfur atoms are treated equivalently (because of their electronegativity). In our simplified model, the coupling to the electrodes is treated through the use of Newns-Anderson chemisorption theory [11], where ideal electrodes are described by constant density of states within energy bandwidth [17-20]. So self-energy matrices (S ) take the diagonal form with elements equal to i 05.0- [eV].Fig.2 Transmission as a function of electron energy (with respect to Fermi energy level)for devices in configuration A (solid curve) and B (broken curve), respectively.Fig.3 Comparison of conductance spectra for devices in configurationA (solid curve) andB (broken curve), respectively. III. Results and discussionNow we proceed to analyze our results from the point of view of quantum interference effects. The geometry of the molecule is taken to be that of anthracene with sulfur atoms on either end of the molecule, binding it to the electrodes in two different configurations – para(A) and meta (B), respectively. For isolated anthracene the HOMO is at 614.7- eV and the LUMO is at 352.5- eV. Because of our simplification that Fermi level is arbitrarily chosen to be located in the middle of the HOMO-LUMO gap, 483.6E F -= eV. The HOMO-LUMO gap for molecular system in para configuration is reduced from 262.2 eV for anthracene to the value of 667.0 eV, but for molecular system in meta configuration it is reduced to zero.Figure 2 shows the transmission dependence on the electron energy for anthracene in para (A) and meta (B) connections with identical electrodes. For transparency we plot it in the logarithmic scale. Asymmetry of the transmission function (with respect to the Fermi energy level) is due to non-orthogonality of atomic orbitals used to describe molecular system. The existence of resonances in the transmission probability is associated with resonant tunneling through molecular eigenstates. Such resonance peaks are shifted and broadened by the fact of the coupling with the electrodes (just like discrete energy levels of the molecule). A change in the configuration of connection between anthracene and two electrodes results in variation of the interference conditions and obvious changes in the transmission function. It manifests itself as shifts in the resonance peaks and in reduction of their height. Well-separated energy levels give rise to distinct peaks in the spectrum, while molecular levels close in energy can overlap and eventually interfere (reduction of resonance peaks is due to destructive interference).Fig.4 Comparison of current-voltage characteristics for devices in configurationA (solid curve) andB (broken curve), respectively.Another remarkable feature of the transmission spectrum is the appearance of antiresonances, which are defined as transmittance zeros and correspond to the physical situation for incident electron being perfectly reflected by a molecule. There are two different mechanisms (well-known in literature) responsible for the origin of antiresonances. One of these is associated with interference between the different molecular orbitals through which the electron propagates [2,21]. The second mechanism is due entirely to the non-orthogonality of atomic orbitals on different atoms [17]. In principle, transport problem in which a non-orthogonal basis set of states is used can be solved by a method proposed recently by Emberly and Kirczenow [5], where condition for antiresonances was analytically demonstrated. However, in this work we perform numerical evaluations of energies at which incoming electron has no chance to leave the source electrode. There are six antiresonances for device in configuration A (F E 821.2E +-=, F E 160.2+-, F E 622.1+-, F E 320.2+,F E 600.3+, F E 907.5+) and only one for device in configuration B (F E E =). Antiresonance is predicted to manifest itself by producing a drop in the differential conductance [5]. Moreover, the fact that it is generated exactly at the Fermi energy of metallic electrodes has important consequences for the conductance spectrum in which antiresonance can be observed (as shown in fig.3). However, in practice this unusual phenomenon can be blurred by some neglected factors which are present in realistic systems, such as: Stark effect, σ states, σ-π hybridization or many-body effects.In figure 4 we plot the current-voltage (I-V) characteristics for both analyzed structures (in para – A and meta – B connections, respectively). The current steps are attributed to the discreteness of molecular energy levels as modified by the coupling with the electrodes [12]. Because this coupling is assumed to be small (bad contacts are suggested by experimental data [1]), the transmission peaks are very narrow and therefore the I-V dependence has a step-like character. In particular, the height of the step in the I-V curve is directly proportional to the area of the corresponding peak in the transmission spectrum. Since quantum interference is important in determining the magnitudes of the resonance peaks, it is also crucial for calculations of the tunneling current. Indeed, the magnitude of the current flowing through the device is very sensitive on the manner of attachment between anthracene molecule and metal surfaces. Large values of the current are predicted for device of configuration A, while reduction of the current by orders of magnitude is expected for device of configuration B (although the shape of the I-V curve is similar in both cases). Such reduction is caused by destructive interference.IV. SummaryIn this paper we have examined the possibility that quantum interference can substantially affect the conductance in molecular-scale devices. The results have shown a striking variation of all the transport characteristics depending on the geometry of the molecular system (its connection with the electrodes). Anyway, the quantum effect of destructive interference may be used within the molecular device to switch its conductivity on and off [8,9]. The existence of interference effects in molecular devices open the question of their control. The phase shift of molecular orbitals could be controlled by a transverse magnetic field or a longitudinal electric field. However, magnetic field seems to be too large to produce significant phase shift (according to our simulations – hundreds of Teslas). AcknowledgmentsAuthor is very grateful to B. Bułka, T. Kostyrko and B. Tobijaszewska for illuminating discussions. Special thanks are addressed to S. Robaszkiewicz for his stimulating suggestions.References1E-mail address: walczak@.pl[1] M. A. Reed, Proc. IEEE 87, 625 (1999) and references therein.[2] P. Sautet, C. Joachim, Chem. Phys. Lett. 153, 511 (1988).[3] V. Marvaud, J. P. Launay, C. Joachim, Chem. Phys. 177, 23 (1993).[4] M. N. Paddon-Row, K. D. Jordan, J. Am. Chem. Soc. 115, 2952 (1993).[5] E. Emberly, G. Kirczenow, J. Phys.: Condens. Matter 11, 6911 (1999).[6] M. Magoga, C. Joachim, Phys. Rev. B 59, 16011 (1999).[7] C. Untiedt, G. Rubio Bollinger, S. Vieira, N. Agraït, Phys. Rev. B 62, 9962 (2000).[8] R. Baer, D. Neuhauser, J. Am. Chem. Soc. 124, 4200 (2002).[9] R. Baer, D. Neuhauser, Chem. Phys. 281, 353 (2002).[10] H. Sellers, A. Ulman, Y. Shnidman, J. E. Eilers, J. Am. Chem. Soc. 115, 9389 (1993).[11] V. Mujica, M. Kemp, M. A. Ratner, J. Chem. Phys. 101, 6849 (1994);ibid. 101, 6856 (1994); ibid. 104, 7296 (1996).[12] S. Datta, Electronic transport in mesoscopic systems, Cambridge University Press,Cambridge 1995.[13] S. Datta, W. Tian, S. Hong, R. Reifenberger, J. I. Henderson, C. P. Kubiak,Phys. Rev. Lett. 79, 2530 (1997).[14] S. N. Yaliraki, A. E. Roitberg, C. Gonzalez, V. Mujica, M. A. Ratner,J. Chem. Phys. 111, 6997 (1999).[15] W. Tian, S. Datta, S. Hong, R. Reifenberger, J. I. Henderson, C. P. Kubiak,J. Chem. Phys. 109, 2874 (1998).[16] E. G. Emberly, G. Kirczenow, Nanotechnology 10, 285 (1999).[17] M. Kemp, A. Roitberg, V. Mujica, T. Wanta, M. A. Ratner,J. Phys. Chem. 100, 8349 (1996).[18] L. E. Hall, J. R. Reimers, N. S. Hush, K. Silverbrook, J. Chem. Phys. 112, 1510 (2000).[19] J. E. Han, V. H. Crespi, Appl. Phys. Lett. 79, 2829 (2001).[20] S. T. Pantelides, M. Di Ventra, N. D. Lang, Physica B 296, 72 (2001).[21] A. Cheong, A. E. Roitberg, V. Mujica, M. A. Ratner,J. Photochem. Photobiol. A 82, 81 (1994).。
标准模型 简化版本
标准模型简化版本The Standard Model is a fundamental theory in particle physics that describes how elementary particles interact with three fundamental forces: electromagnetism, the weak nuclear force, and the strong nuclear force. 标准模型是粒子物理中的一个基础理论，描述了基本粒子如何与三种基本力相互作用：电磁力、弱核力和强核力。
The Standard Model is a mathematical framework that has successfully predicted the existence of various particles, such as the Higgs boson, which was discovered at CERN in 2012. 标准模型是一个成功预测了各种粒子存在的数学框架，比如在2012年在欧洲核子研究中心发现的希格斯玻色子。
One of the key components of the Standard Model is the classification of elementary particles into two categories: fermions and bosons. Fermions are the building blocks of matter and include quarks and leptons, while bosons are force carriers, such as the photon and the W and Z bosons. 标准模型的关键组成部分之一是将基本粒子分为两类：费米子和玻色子。
物理专业常用英语词汇
物理：absolute acceleration 绝对加速度absolute error 绝对误差absolute motion 绝对运动absolute temperature 绝对温度absolute velocity 绝对速度absolute zero 绝对零度absorption 吸收absorptivity 吸收率accelerated motion 加速运动acceleration of gravity 重力加速度acceleration 加速度accidental error 偶然误差acoustics 声学acting force 作用力adjustment 调节aether 以太air pump 抽气机air table 气垫桌air track 气垫导轨alternating current circuit 交流电路alternating current generator 交流发电机alternating current 交流电altimeter 测高仪ammeter 安培计amperemeter 电流计ampere 安培Ampere's experiment 安培实验Ampere's force 安培力Ampere's law 安培定律amperemeter 安培计amplitude 振幅angle of rotation 自转角，转动角angular acceleration 角加速度angular displacement 角位移angular velocity 角速度anion 负离子anisotropy 各向异性annihilation 湮没anode 阳极antenna 天线applied physics 应用物理学Archimedes principle 阿基米德原理area 面积argumentation 论证argument 辐角astigmatoscope 散光镜atomic nucleus 原子核atomic physics 原子物理学atomic spectrum 原子光谱atomic structure 原子结构atom 原子Atwood ' s machine 阿特伍德机average power 平均功率average velocity 平均速度Avogadro constant 阿伏加德罗常数Avogadro law 阿伏加德罗定律balance 天平ballistic galvanometer 冲击电流计band spectrum 带状谱barometer 气压计basic quantity 基本量basic units 基本单位battery charger 电池充电器battery,accumulator 蓄电池battery 电池组beam 光束betatron 电子感应加速器Bohr atom model 玻尔原子模型boiling point 沸点boiling 沸腾bounce 反弹bound charge 束缚电荷bound electron 束缚电子branch circuit 支路breakdown 击穿brightness 亮度buoyancy force 浮力calorifics 热学camera 照相机capacitance 电容capacitor 电容器capillarity 毛细现象cathode ray 阴极射线cathode-ray tube 阴极射线管cathode 阴极cation 正离子cell 电池Celsius scale 摄氏温标centre of gravity 重心centre of mass 质心centrifugal force 离心力centripetal acceleration 向心加速度centripetal force 向心力chain reaction 链式反应chaos 混沌characteristic spectrum 特征光谱charged body 带电体charged particle 带电粒子charge 充电circular hole diffraction 圆孔衍射circular motion 圆周运动classical mechanics 经典力学classical physics 经典物理学cloud chamber 云室coefficient of maximum staticfriction 最大静摩摩系数coefficient of restitution 恢复系数coefficient of sliding friction 滑动摩擦系数coefficient 系数coherent light 相干光源coil 线圈collision 碰撞component force 分力component velocity 分速度composition of forces 力的合成composition of velocities 速度的合成compression 压缩concave lens 凹透镜concave mirror 凹面镜concurrent force 共点力condensation 凝结condenser 电容器conducting medium 导电介质conductor 导体conservative force field 保守力场conservative force 保守力constant force 恒力constant 常量continuous spectrum 连续谱convergent lens 会聚透镜convex lens 凸透镜convex mirror 凸面镜coordinate system 坐标系coplanar force 共面力Corolis force 科里奥利力corpuscular property 粒子性corpuscular theory 微粒说Coulomb force 库仑力coulomb 库仑Coulomb's law 库仑定律counter 计数器creation 产生creepage 漏电crest 波峰critical angle 临界角critical resistance 临界电阻critical temperature 临界温度crystal 晶体current density 电流密度current element 电流元current source 电流源current strength 电流强度curvilinear motion 曲线运动cyclotron 回旋加速器damped vibration 阻尼振动damping 阻尼Daniell cell 丹聂耳电池data processing 数据处理data 数据decay 衰变definition of ampere 安培的定义defocusing 散集density 密度derived quantity 导出量derived unit 导出单位dielectric 电介质diffraction pattern 衍射图样diffraction 衍射diffuse reflection 漫反射digital timer 数字计时器dimensional exponent 量纲指数dimension 量纲diode 二级管diopter 屈光度direct current, DC 直流direct impact 正碰direct measurement 直接测量discharge 放电disorder 无序dispersion 色散displacement 位移divergent lens 发散透镜Doppler effect 多普勒效应double slit diffraction 双缝衍射driving force 驱动力dry cell 干电池echo 回声eddy current 涡流effective value 有效值elastic body 弹性体elastic force 弹［性］力elasticity 弹性electric charge 电荷electric circuit 电路electric corona 电晕electric energy 电能electric field 电场electric field intensity 电场强度electric field line 电场线electric flux 电通量electric leakage 漏电electric neutrality 电中性electric potential 电位，电势electric potential difference 电位差，电势差electric potential energy 电位能electric power 电功率electric quantity 电量electrification 起电electrification by friction 摩擦起电electrified body 带电体electrode 电极electrolysis 电解electrolyte 电解质electromagnetic damping 电磁阻尼electromagnetic induction 电磁感应electromagnetic radiation 电磁辐射electromagnetic wave 电磁波electromagnetic wave spectrum 电磁波谱electromagnetism induction phenomenon 电磁感应现象electromagnet 电磁体electrometer 静电计electromotive force 电动势electron 电子electron beam 电子束electron cloud 电子云electron microscope 电子显微镜electron volt 电子伏特electroscope 验电器electrostatic equilibrium 静电平衡electrostatic induction 静电感应electrostatic screening 静电屏蔽elementary charge 基本电荷，元电荷energy 能量energy level 能级equilibrium 平衡equilibrium condition 平衡条件equilibrium of forces 力的平衡equilibrium position 平衡位置equilibrium state 平衡态equivalent source theorem 等效电源定理erect image 正像error 误差ether 以太evaporation 蒸发excitation 激发excitation state 激发态experiment 实验experimental physics 实验物理学external force 外力eyepiece 目镜far sight 远视Faraday cylinder 法拉第圆筒Faraday law ofelectromagnetic induction 法拉第电磁感应定律Faraday's law ofelectromagnetic induct 法拉第电磁感应定律farad 法拉(电容的单位)film interference 薄膜干涉final velocity 末速度first cosmic velocity 第一宇宙速度fission 裂变fixed-axis rotation 定轴转动flotation balance 浮力秤fluid 流体focal length 焦距focusing 调焦，聚焦focus 焦点force 力forced vibration 受迫振动fractal 分形free charge 自由电荷free electron 自由电子free period 自由周期freezing point 凝固点frequency 频率friction force 摩擦力fusion 聚变galvanometer 电流计gas 气体general physics 普通物理学generator 发电机good conductor 良导体gravitation 引力gravity 重力gravitational potential energy重力势能gravity field 重力场ground earth 接地ground state 基态ground wire 地线hadron 强子half life period 半衰期heat 热heat transfer 传热henry 亨利hertz 赫兹(频率的单位)Hooke law 胡克定律humidity 湿度hydrogen 氢原子hypothesis 假设ice point 冰点ideal gas 理想气体image 像image distance 像距image height 像高imaging 成像imperfect inelastic collision 非完全弹性碰撞impulse 冲量incident angle 入射角incident ray 入射线indirect measurement 间接测量induced electric current 感应电流induced electric field 感应电场induction current 感应电流induction electromotive force感应电动势induction motor 感应电动机inertia 惯性inertial force 惯性力inertial system 惯性系infrared ray 红外线infrasonic wave 次声波initial phase 初位相initial velocity 初速度input 输入instantaneous power 瞬时功率instantaneous velocity 瞬时速度instrument 仪器insulated conductor 绝缘导体insulating medium 绝缘介质insulator 绝缘体intensity of sound 声强interference 干涉interference fringe 干涉条纹interference pattern 干涉图样interferometer 干涉仪internal energy 内能internal force 内力internal resistance 内阻intonation 声调inverted image 倒像invisible light 不可见光ion beam 离子束ionization 电离irreversible process 不可逆过程isobaric process 等压过程isobar 等压线isochoric process 等体积过程isothermal 等温线isothermal process 等温过程isotope 同位素isotropy 各向同性joule 焦耳（功的单位）Joule heat 焦耳热Joule law 焦耳定律Joule' law 焦耳定律Kepler law 开普勒定律kinematics 运动学kinetic energy 动能Laplace's equation 拉普拉斯方程laser 激光，激光器law 定律law of conservation of angular momentum 角动量守恒定律law of conservation of energy 能量守恒定律law of conservation of mass 质量守恒定律law of conservation of mechanical energy 机械能守恒定律law of conservation of momentum 动量守恒定律law of electric charge conservation 电荷守恒定律Le Système International d ` Unit è s 国际单位制(SI)lead 导线length 长度lens 透镜lens formula 透镜公式Lenz's law 楞次定律lepton 轻子Light ray 光线light source 光源light wave 光波lightning rod 避雷针light 光line spectrum 线状谱lines of current 电流线lines of force of electric field 电力线liquefaction 液化liquefaction point 液化点liquid 液体longitudinal wave 纵波loop 回路Lorentz force 洛仑兹力luminous intensity 发光强度magnetic field 磁场magnetic field intensity 磁场强度magnetic field line 磁场线magnetic induction flux 磁感应通量magnetic induction 磁感应强度magnetic induction line 磁感应线magnetic material 磁性材料magnetic needle 磁针magnetic pole 磁极magnetics 磁学magnetism 磁学magnetization 磁化magnet 磁体magnification 放大率magnifier 放大镜，放大器manometer 流体压强计mass 质量mass defect 质量亏损mass-energy equation 质能方程matter 物质matter wave 物质波Maxwell's equations 麦克斯韦方程组mean speed 平均速率mean velocity 平均速度measurement 测量mechanical energy 机械能mechanical motion 机械运动mechanical vibration 机械振动mechanics 力学medium 介质melting fusion 熔化melting point 熔点metre rule 米尺microdetector 灵敏电流计micrometer caliper 螺旋测微器microscope 显微镜microscopic particle 微观粒子mirror reflection 镜面反射mirror 镜mixed unit system 混合单位制modern physics 现代物理学molar volume 摩尔体积molecular spectrum 分子光谱molecular structure 分子结构moment of force 力矩momentum of electromagneticfield 电磁场的动量momentum 动量motor 电动机multimeter 多用［电］表musical quality 音色N pole 北极natural frequency 固有频率natural light 自然光negative charge 负电荷negative crystal 负晶体negative ion 负离子negative plate 负极板network 网络neutralization 中和neutron 中子newton 牛顿（力的单位）Newton first law 牛顿第一定律Newton second law 牛顿第二定律Newton third law 牛顿第三定律nonequilibrium state 非平衡态north pole 北极nucleus force 核力nucleus of condensation 凝结核object 物object distance 物距object height 物高objective 物镜observation 观察Oersted's experiment 奥斯特实验ohm 欧姆Ohm law 欧姆定律ohmmeter 欧姆计Ohm's law 欧姆定律open circuit 开路optical bench 光具座optical centre of lens 透镜光心optical fiber 光导纤维optical glass 光学玻璃optical instrument 光学仪器optical lever 光杠杆optical path difference 光程差optical path 光程(路)optically denser medium 光密介质optically thinner medium 光疏介质optics 光学orbit 轨道order 有序oscillograph 示波器output 输出overweight 超重parallel connection ofcondensers 电容器的并联parallelogram rule 平行四边形定律parallel-resonance circuit 并联谐振电路parameter 参量particle 质点，粒子Pascal law 帕斯卡定律path 路程peak 峰值pendulum 摆penumbra 半影perfect conductor 理想导体perfect elastic collision 完全弹性碰撞perfect inelastic collision 完全非弹性碰撞periodicity 周期性period 周期periscope 潜望镜permanent magnet 永磁体permittivity of vacuum 真空介电常数permittivity 电容率phase 位相phenomenon 现象photocurrent 光电流photoelectric cell 光电管photoelectric effect 光电效应photoelectron 光电子photography 照相术photon 光子physical balance 物理天平physical quantity 物理量physics 物理学piezometer 压强计pitch 音调Planck constant 普朗克常量plasma 等离子体point charge 点电荷polarization 偏振polarized light 偏振光polycrystal 多晶体poor conductor 不良导体positive charge 正电荷positive crystal 正晶体positive ion 正离子positive plate 正极板positron 正电子potential energy 势能potentiometer 电位差计power 功率pressure 压强，压力primary coil 原线圈principle of constancy of light velocity 光速不变原理prism 棱镜projectile 抛体projectile motion 抛体运动projector 投影仪proton 质子pulley 滑轮pulley block 滑轮组quantity of heat 热量quantization 量子化quantum 量子quantum mechanics 量子力学quantum number 量子数radar 雷达radioactive source 放射源radius of gyration 回旋半径random motion 无规则运动range 量程rated voltage 额定电压reacting force 反作用力real image 实像real object 实物reasoning 推理recoil 反冲rectilinear motion 直线运动reference frame 参考系，坐标系reference system 参考系reflected angle 反射角reflected ray 反射线reflection coefficient 反射系数reflection law 反射定律reflectivity 反射率refracted angle 折射角refracted ray 折射线refraction law 折射定律refraction coefficient 折射系数refractive index 折射率relative acceleration 相对加速度relative error 相对误差relative motion 相对运动relative velocity 相对速度relativity 相对论resistance 电阻resistance box 电阻箱resistivity 电阻率resistor 电阻［器］resolution of force 力的分解resolution of velocity 速度的分解resonance 共振，共鸣resonant frequency 共振频率resultant force 合力resultant velocity 合速度reversibility of optical path 光路可逆性reversible process 可逆过程rheostat 变阻器right-hand screw rule 右手螺旋定则rocker 火箭rotating magnetic field 旋转磁场rotation 自转，转动Rutherford scattering 卢瑟福散射Rutherford ［α-particlescattering］experiment 卢瑟福［α散射］实验S pole 南极saturation 饱和scalar 标量scalar field 标量场scanner 扫描器second cosmic velocity 第二宇宙速度selective absorption 选择吸收self-induced electromotiveforce 自感电动势self-inductance 自感self-induction phenomenon 自感系数semiconductor 半导体semi-transparent film 半透膜sensitive galvanometer 灵敏电流计sensitivity 灵敏度sensitometer 感光计sensor 传感器series connection ofcondensers 电容器的串联series-resonance circuit 串联谐振电路short circuit 短路short sight 近视shunt resistor 分流电阻significant figure 有效数字simple harmonic motion (SHM)简谐运动simple harmonic wave 简谐波simple pendulum 单摆single crystal（monocrystal）单晶体single slit diffraction 单缝衍射sinusoidal alternating current简谐交流电sinusoidal current 正弦式电流sliding friction 滑动摩擦slit 狭缝solar cell 太阳能电池solenoid 螺线管solidification 凝固solidifying point 凝固点solid 固体solution 溶液solvation 溶解sonar 声纳sound source 声源sound velocity 声速sound wave 声波sound 声［音］source 电源south pole 南极space 空间spark discharge 火花放电special relativity 狭义相对论specific heat capacity 比热容spectacles 眼镜spectral analysis 光谱分析spectral line ［光］谱线spectrograph 摄谱仪spectrography 摄谱学spectroscopy 光谱学spectrum 光谱speed 速率spherical mirror 球面镜spontaneous radiation 自发辐射spring balance 弹簧秤stability 稳定性stabilized current supply 稳流电源stabilized voltage supply 稳压电源standard atmosphericpressure 标准大气压standard cell 标准电池standing wave 驻波static friction 静摩擦stationary state 定态steady current 恒定电流steady current source 恒流源steady voltage source 恒压源steam point 汽点stiffness 劲度［系数］stimulated radiation 受激辐射stop watch 停表sublimation 升华superconductivity 超导［电］性superconductor 超导体superposition principle ofelectric field 电场强度叠加原理superposition theorem 叠加定律supersaturation 过度饱和supersonic speed 超声速supersonic wave 超声波supply transformer 电源变压器surface resistance 表面电阻switch 开关system of concurrent forces 共点力系system of particles 质点系system of units 单位制systematic error 系统误差telescope 望远镜temperature 温度tension 张力the law of gravity 万有引力定律theorem 原理theorem of kinetic energy 动能定理theorem of momentum 动量定理theoretical physics 理论物理学theory 理论thermal capacity 热容［量］thermal equilibrium 热平衡thermal motion 热运动thermal transmission 传热thermodynamic scale ［of temperature］热力学温标thermodynamic temperature 热力学温度thermometer 温度计thermometric scale 温标thermonuclear reaction 热核反应thick lens 厚透镜thin lens 薄透镜third cosmic velocity 第三宇宙速度three-phase alternating current 三相［交变］电流time 时间timer 定时器，计时器torsion balance 扭秤total reflection 全反射trajectory 轨道transformer 变压器transistor 晶体管transition 跃迁translation 平移transmission line 传输线transmissivity 透射率transverse wave 横波triboelectrification 摩擦起电triode 三极管trough 波谷tuning fork 音叉turbulent flow 湍流ultrasound wave 超声波ultraviolet ray 紫外线umbra 本影undulatory property 波动性uniform dielectric 均匀电介质uniform motion 匀速运动unit 单位unit system 单位制universal constant 普适常量universal gravitation 万有引力universal meter 多用［电］表vacuum tube 真空管vacuum 真空value of amplitude 幅值vaporization 汽化variable 变量vector 矢量velocity of light 光速velocity 速度verification 验证vernier 游标vernier caliper 游标卡尺vibration 振动viewing angle 视角viewing field 视场virtual image 虚像virtual object 虚物virtual value 有效值visibility 可见度visible light 可见光voltage 电压voltage division circuit 分压电路voltaic cell 伏打电池voltmeter 伏特计voltmeter-ammeter method伏安法volt 伏特volume 体积vortex electric field 涡旋电场watt 瓦特wave equation 波动方程wave theory 波动说wavelength 波长wave-particle dualism 波粒二象性wave 波weight 重量weightlessness 失重white light 白光work 功work function 逸出功X-ray X射线Young experiment 杨氏实验zero line 零线α -decay α衰变α -particle α粒子α -ray α射线β -decay β衰变β -ray β射线γ -decay γ衰变γ -ray γ射线。
原子核模型及其发展
原子核模型及其发展英文回答：The atomic nucleus model is a scientific theory that describes the structure and behavior of the nucleus, whichis the central part of an atom. The development of this model has evolved over time through the contributions of various scientists.One of the earliest models of the atomic nucleus was proposed by Ernest Rutherford in 1911. He conducted the famous gold foil experiment, in which he bombarded a thin sheet of gold foil with alpha particles. Rutherfordobserved that most of the particles passed through the foil, but a small fraction of them were deflected at large angles. This led him to conclude that the atom has a tiny, dense, and positively charged nucleus at its center, surrounded by a cloud of negatively charged electrons.Rutherford's model was further refined by Niels Bohr in1913. Bohr introduced the concept of energy levels or shells, in which electrons orbit the nucleus at specific distances. He proposed that electrons can only exist in these discrete energy levels and that they can jump between levels by absorbing or emitting energy in the form of photons. This model explained the stability of atoms and the observed emission and absorption spectra.However, the Bohr model was limited in its ability to explain the behavior of larger atoms. It failed to account for the fine details of atomic spectra and the behavior of electrons in more complex atoms. To address these limitations, the quantum mechanical model of the atomic nucleus was developed.The quantum mechanical model, also known as the electron cloud model, was proposed by Erwin Schrödinger and Werner Heisenberg in the 1920s. This model describes the behavior of electrons as wave-like particles in athree-dimensional region around the nucleus called an atomic orbital. The probability of finding an electron in a particular region is represented by a mathematical functionknown as the wave function.The development of the atomic nucleus model has revolutionized our understanding of the microscopic world.It has provided insights into the structure and behavior of atoms, as well as the basis for understanding chemical reactions and the properties of materials. For example, the understanding of atomic structure has led to the development of various technologies, such as nuclear power and medical imaging.中文回答：原子核模型是描述原子核结构和行为的科学理论，原子核是一个原子的中心部分。