Cs 39D态Rydberg原子Stark光谱的实验研究

本文从理论和实验上对Cs39D态Rydberg原子在弱电场作用下的Stark效应做了详细研究. 理论上利用数值方法计算了Cs原子39D态的Stark结构;实验上,采用两步激发超冷基态原子获得超冷Rydberg原子,通过场电离的方法获得了39D态的Stark光谱,测量获得α^5/2₂,α^5/2₀,α^3/2₂和α^3/2₀相应的极化率分别为：62(7),－146(13), 73(6) 和－106(20) MHz·V^-2cm²,实验结果与理论相符合.     

C2H2分子受激Raman光谱中的光学Stark效应研究

本文研究了C₂H₂分子受激Raman光谱(SRS)中的光学斯塔克(Stark)效应,同时还研究了激光功率以及单一转动态量子数J与Stark效应的关系.实验表明:C₂H₂分子在高强度激光电场作用下,它的SRS由于光学Stark效应产生明显的非对称加宽,利用Stark线型加宽数值模拟,从理论上计算了Raman光谱线型,与实验的SRS线型比较,二者符合程度相当好.     

镁原子碰撞激发微分截面和Stokes参数的理论研究

基于相对论扭曲波理论方法,并利用新发展的处理极化电子碰撞激发的计算程序REIE06, 系统计算了中性镁原子基态3s^{2 1}S₀到激发态3s3p ¹P₁, 3s4p ¹P₁的电子碰撞激发微分截面和角关联(Stokes)参数,计算过程中系统地考虑了相对论效应、电子关联效应等. 部分计算结果与已有的实验和理论结果进行了比较,得到了较好的一致性.     

β-Si3N4电子结构和红外和拉曼频率的第一性原理研究

分别用PW91，B3LYP两种密度泛函方法和全电子高斯基组对β-Si₃N₄的几何结构进行全优化(包括晶格参数和原子坐标)，结果和实验值符合良好. 同时计算了能带结构和态密度.在此基础上分别用上述两种方法计算了Γ点拉曼振动频率，并按对称性进行分类，将得到的11种拉曼活性模式的频率值与实验值以及其他文献值进行了比较，进一步确定了A_g模式为中等频率，值约459cm^-1. 计算结果表明     

静电场中Ca原子里德堡态的能级结构

用两步激发和光电离方法,在0—8kV/cm电场范围内,测定了Ca原子n=10至n=13附近m=0的Stark光谱。实验结果显示,3d²³P₀及3d²³P₂价态受到n=12Stark簇的排斥。观察到与价态有关的干涉现象及其随电场大小的改变。讨论了零场非简并态、价态及Stark簇之间的能级交叉和抗交叉结构。     

锶原子三重态谱线的观测及在光钟中的应用

实验中通过互组跃迁689 nm激光抽运形成三重态最低能态原子布居,引入688 nm激光改变三重态最低能态间的原子布居,利用抽运光与探测光空间分离的方法观测碱土金属锶原子的三重态能态间跃迁(5s6s)³S₁ → (5s5p)³P_j(j=0,1,2)的吸收谱线,对应三条跃迁线的激光波段为679 nm, 688 nm和707 nm.探测三重态原子跃迁谱线可以用于锶原子冷却中再抽运光707 nm和679 nm激光频率的直接锁定,相比于通常利用的腔传递技术,可以把再抽运光频率锁定在原子跃迁谱线上,有利于提高锶原子冷却中俘获原子数目的长期稳定性.     

虚晶近似法研究AlN-Al2O3固溶体系的力学性能和电子结构

基于密度泛函理论的第一性原理平面波赝势方法, 运用虚晶近似方法计算了AlN-Al₂O₃固溶区内尖晶石相氮氧化铝(Al₂₄O₂₄N₈, Al₂₃O₂₇N₅和Al₂₂O₃₀N₂)和α-Al₂O₃, AlN的力学性能和电子结构. 结果证明虚晶近似法应用到氮氧化铝结构计算中是可行的. 力学常数计算结果和弹性模量B, 剪切模量G, 杨氏模量E反映的材料硬度变化趋势与实验基本一致;Al₂O₃-AlN固 溶区内五种结构均为脆性性质且Al₂₃O₂₇N₅脆性最低, 硬度高、脆性低的特性反映了Al₂₃O₂₇N₅优异的抗弯强度性能. 五种结构满足力学结构上的稳定性, 立方尖晶石相氮氧化铝表现为弹性各向异性. 能带和态密度的计算分析表明这五种结构均为直接宽带隙结构. 在费米能级附近, 氮氧化铝结构中阴离子的2p态和阳离子的3s, 3p态发生了轨道杂化. 理论结果与实验数据基本符合, 为进一步研究提供了一定的理论方法和依据.     

YH,YD,YT分子基态的结构与势能函数

在Y的有效核势近似下, 对H分别选6-311++G(3df,2pd), AUG-cc-PVTZ, AUG-cc-PVQZ基组, 应用密度泛函理论的B3LYP方法, 优化计算了YH(D,T)分子基态的能量, 平衡结构, 和谐振频率.根据原子分子反应静力学原理, 导出了YH(D,T)分子基态的合理离解极限. 通过优化计算结果和已有的实验和理论数据对比, 得出LANL2TZ/AUG-cc-PVQZ混合基组为对体系进行计算的最优基组. 基于此, 在B3LYP/LANL2TZ/AUG-cc-PVQZ水平对YH(D,T)分子基态的势能面进行了单点能扫描. 并采用最小二乘法拟合得到了相应的Murrell-Sorbie势能函数. 计算出了这些分子的力常数(f₂, f₃, f₄)和光谱常数(B_e, α_e, ω_e, ω_eχ_e, D_e).结果与已有的实验数据符合得很好.     

NaBn(n=1—9)团簇的几何结构和电子性质

应用密度泛函理论(DFT)中B3LYP方法在6-311+G(d)水平上计算并分析了 NaB_n(n=1—9)团簇的几何结构及电子性质. 同时, 讨论了团簇的平均结合能、能级间隙、二阶能量差分和极化率.研究表明:NaB_n(n=1—9) 团簇基态绝大多数为平面构型. 能级间隙和二阶能量差分结果表明NaB₃与NaB₅是幻数团簇. 另外, 对平均线性极化率和极化率的各向异性不变量研究表明基态NaB_n团簇的电子结构随B原子的增加虽然趋于紧凑, 但尚未形成特定的堆积方式.     

内掺过渡金属非典型富勒烯M@C22(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni) 几何结构、电子结构、稳定性和磁性的密度泛函研究

采用密度泛函理论中广义梯度近似对非典型富勒烯C₂₂和过渡金属内掺衍生物M@C₂₂(M=Sc,Ti,V,Cr,Mn,Fe,Co和Ni)的几何结构和电子结构进行计算研究.发现非典型富勒烯C₂₂的基态结构是含有一个四碳环的单重态笼状结构.过渡金属原子的掺入明显提高了体系的稳定性. C-M键既有一定共价性又有一定离子性.磁性、能级图、轨道分布和态密度图分析表明: M原子的3d轨道和碳笼的C原子的原子轨道之间存在较强的轨道杂化. Ti, Cr, Fe和Ni内掺的结构出现磁性完全猝灭现象. Sc和碳笼间是弱反铁磁作用, V,Mn和Co与碳笼间是弱铁磁作用.     

Measurement of the electric dipole moment of NO (X2 Π ν = 0,1) by mid-infrared laser magnetic resonance spectroscopy

A pair of parallel Stark plates are added to a CO laser magnetic resonance spectrometer to apply electric field in the absorption cell. This apparatus is used to measure the molecular electric dipole moment via Zeeman and Stark effects simultaneously. The saturated absorption spectra of NO (X²Π_3/2, ν = 1 ← 0) was observed and the electric dipole moments of NO were directly measured in the presence of an electric field. The dipole moments are determined as μ₀(ν = 0) = 0.1595(15) D, μ₁ (ν = 1) = 0.1425(16) D. The electric dipole moment of the vibrationally excited state (ν = 1) is determined for the first time. The dependence of the electric dipole moments on its nuclear distances is interpreted.     

Electric dipole moments of lithium atoms in Rydberg states

Recently, the diverse properties of Rydberg atoms, which probably arise from its large electric dipole moment(EDM),have been explored. In this paper, we report electric dipole moments along with Stark energies and charge densities of lithium Rydberg states in the presence of electric fields, calculated by matrix diagonalization. Huge electric dipole moments are discovered. In order to check the validity of the EDMs, we also use these electric dipole moments to calculate the Stark energies by numerical integration. The results agree with those calculated by matrix diagonalization.     

Effect of external electric field on R line absorption spectra in LiNbO3:Cr3+ crystals

The effect of an external electric field on the R absorption lines of LiNbO₃:Cr³⁺ crystals has been studied by a high-sensitivity differential technique at 77 K. Linear Stark effect has been observed in a field directed along the trigonal crystal axis. No effect of the field was observed when directed perpendicular to this axis. These characteristics of the Stark effect provide a convincing argument for the electric dipole moments of Cr³⁺ centers being oriented along the trigonal C ₃ axis of the crystal and indicate that the chromium centers in LiNbO₃ have C ₃ symmetry. Fiz. Tverd. Tela (St. Petersburg) 39, 2053–2056 (November 1997)     

外电场下BH分子势能函数

运用密度泛函B3P86方法和cc-PV5Z基组,获得了BH分子基态在不同外电场下的键长、偶极矩和振动频率等物理性质参数.通过分析物理性质参数,判断离解电场所处的范围,设置合适的参数扫描该范围的单点能获得势能曲线.结果表明物理性质参数和势能值随外电场的变化而变化,特别是在反向电场中.利用Morse势模型拟合无外场下势能函数,得到的拟合参数与实验值吻合较好,采用偶极近似构建外电场下的势能函数模型,编制程序拟合对应的势能函数,得出拟合参数,再计算临界离解电场参量,结果与数值计算值较为一致,说明构建的模型是可靠和准确的.为分析外场下分子光谱、动力学特性和分子Stark效应冷却囚禁提供理论参考.     

Properties of a Si2N molecule under an external electric field

In the present work,we adopt the ccsd/6-31g（d） method to optimize the ground state structure and calculate the vibrational frequency of the Si2N molecule.The calculated frequencies accord satisfactorily with the experimental values,which helps confirm the ground state structure of the molecule.In order to find how the external electric field affects the Si2N molecule,we use the density functional method B3P86/6-31g（d） to optimize the ground state structure and the time-dependent density functional theory TDDFT/6-31g（d） to study the absorption spectra,the excitation energies,the oscillator strengths,and the dipole moments of the Si2N molecule under different external electric fields.It is found that the absorption spectra,the excitation energies,the oscillator strengths,and the dipole moments of the Si2N molecule are affected by the external electric field.One of the valuable results is that the absorption spectra of the yellow and the blue-violet light of the Si2N molecule each have a red shift under the electric field.The luminescence mechanism in the visible light region of the Si2N molecule is also investigated and compared with the experimental data.     

Pair production and vacuum polarization of vector particles with electric dipole moments and anomalous magnetic moments

The matrix 8-component Dirac-like form of the P-odd equations for boson fields of spin 1 and 0 are obtained and the symmetry group of the equations is derived. We found exact solutions of the field equation for vector particles with arbitrary electric and magnetic moments in external constant and uniform electromagnetic fields. The differential probability of pair production of vector particles with electric dipole moments and anomalous magnetic moments by an external constant and uniform electromagnetic field has been found using exact solutions. We have calculated the imaginary and real parts of the electromagnetic field Lagrangian that takes into account the vacuum polarization of vector particles. Received: 14 April 2001 / Revised version: 13 July 2001 / Published online: 19 September 2001     

Evaluation and properties of a model for the determination of internal electric fields in proteins from the Stark effect of spectral holes

In this paper, we further evaluate a model for the analysis of Stark-shifted spectral holes, which allows for the determination of electric fields generated at the site of probe molecules by their host environment. In contrast to the conventional treatment of the Stark effect, our model regards both the internal electric field and the externally applied electric field as perturbations to the Hamiltonian of the probe molecule. Diagonalization of the Hamiltonian and fitting to the Stark-shifted spectral holes allows for the extraction of the internal electric field. We apply this model to Stark-shifted spectral holes burnt in a biological system, namely, myoglobin. Determining internal electric fields at the active sites of biological systems is particularly interesting, as these fields may contribute substantially to the function of such systems. As input to the data analysis procedure, state energies, transition dipole moments, and the local field factor are needed. We demonstrate here how the number of electronic states, the choice of local field factor, and the energies of several excited states of the probe molecule affect the resulting internal electric fields.     

Electric dipole moments of acrylonitrile and of propionitrile measured in supersonic expansion

New determinations of the ground-state electric dipole moments of acrylonitrile and propionitrile have been made from Stark effect measurements at conditions of supersonic expansion. The measurements were made on selected Stark lobes of fully resolved hyperfine components of several lowest-J rotational transitions. The results are μ_a = 3.821(3) D, μ_b = 0.687(8) D, μ_tot = 3.882(3) D for acrylonitrile, and μ_a = 3.816(3) D, μ_b = 1.235(1) D, μ_tot = 4.011(3) D for propionitrile. The new value of μ_b for acrylonitrile is appreciably different from those reported previously and it has been substantiated by both ab initio calculations and relative intensity measurements. The new dipole moment implies a considerable revision in the calculated intensities of the strongest THz-region rotational transitions of acrylonitrile, to 59% of previous values.     

外电场对BeH分子结构和势能函数的影响

采用密度泛函B3P86方法,结合Dunning的相关一致五重基cc-PV5Z,设置不同的外电场参量进行优化计算,获得了不同外电场下Be H分子的键长、偶极矩、振动频率和红外光谱等物理性质参数.通过分析参数随外电场的变化关系,判断离解电场所处的范围,设置合适的外电场参数,采用单双取代耦合团簇CCSD(T)方法,扫描计算该范围的单点能获得其势能曲线.结果分析表明物理性质参数和势能随外电场的变化而变化,且外加反向电场时变化幅度更大.采用偶极近似构建外电场下的势能函数模型,编制程序拟合对应的势能函数,得出拟合参数,进而计算临界离解电场参量,结果与数值计算和理论分析较为一致,说明构建的模型是合理和可靠的.这为分析外场下分子光谱、动力学特性和分子Stark效应冷却囚禁提供重要的理论和实验参考.     

外电场对BeH分子结构和势能函数的影响

采用密度泛函B3P86方法, 结合Dunning的相关一致五重基,设置不同的外电场参量进行优化计算,获得了不同外电场下BeH分子的键长、偶极矩、振动频率和红外光谱等物理性质参数. 通过分析参数随外电场的变化关系,判断离解电场所处的范围,设置合适的外电场参数,采用单双取代耦合团簇方法,扫描计算该范围的单点能获得其势能曲线. 结果分析表明物理性质参数和势能随外电场的变化而变化,且外加反向电场时变化幅度更大.采用偶极近似构建外电场下的势能函数模型,编制程序拟合对应的势能函数,得出拟合参数,进而计算临界离解电场参量,结果与数值计算和理论分析较为一致,说明构建的模型是合理和可靠的.这为分析外场下分子光谱、动力学特性和分子Stark效应冷却囚禁提供重要的理论和实验参考.