几种香豆素衍生物分子的二阶非线性光学性质的从头算研究

采用从头算ab initio Hartree_Fock/6_31G方法，对以3_苯基香豆素为母体的香豆素系列衍生物分子进行了几何优化，计算了它们的分子二阶非线性光学系数β值，分析了其分子结构、取代基类型和取代位置对β值的影响，并对计算结果所反映的规律性进行了探讨. 关键词： 3_苯基香豆素 非线性光学 二阶效应 从头算 电荷转移     

Electronic polarizabilities of ions in II–VI crystals

The electronic polarizabilities of O^2?, S^2?, Se^2? and Te^2? ions are reported for the first time using two models, an additive law and an interaction law. The calculations show that the additive law does not hold good for II–VI group compounds, and therefore, one has to include some sort of interaction term to calculate the polarizabilities of these ions.     

Electronic polarizabilities and sizes of ions in AN B10−N type semiconductors

Electronic polarizabilities and sizes of ions in A^N B^10?N type semiconductors (PbS, PbSe, PbTe and SnTe) have been deduced in the present study. The free ion polarizabilities of Sn²⁺ and Pb²⁺ ions are estimated approximately following the procedure of Pauling. The effect of crystalline potential is then estimated on free cation polarizabilities. An empirical relation between ionic radii and polarizabilities has been applied to deduce the ionic sizes and anion polarizabilities. The calculated molecular electronic polarizabilities agree well with the experimental values. The variation of dielectric constant with strain has also been estimated in each crystal and the results are explained in terms of the optical anisotropy parameter.     

Measurement of the proton spin polarizabilities at MAMI

The spin polarizabilities of the nucleon are fundamental structure constants which describe the response of the nucleon spin to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is the Compton scattering with polarization degrees of freedom. Three Compton scattering asymmetries on the proton were measured in the Δ(1232) region using a polarized incident photon beam and a polarized (or unpolarized) proton target at the Mainz Microtron (MAMI). These asymmetries are sensitive to values of the spin polarizabilities. Fits to asymmetry data were performed using a dispersion model calculation, and a separation of all four proton spin-polarizabilities in the multipole basis was achieved. The values of the proton spin polarizabilities are presented.     

Effect of the crystal potential on electronic polarizabilities of ions in alkaline earth chalcogenides

The electronic polarizabilities of ions in alkaline earth chalcogenides are estimated by taking account of the effect of the crystalline potential. The polarizabilities thus obtained are found to present a good agreement with experimental data. It has been shown that the polarizabilities and radii of alkaline earth and chalcogenide ions follow the polarizability-radius cube relation approximately well.     

手性分子2, 3-丁二醇的旋光拉曼光谱研究

本文从拉曼峰和旋光拉曼峰出发,通过键极化率和微分键极化率分析研究(2R, 3R)-2, 3-丁二醇. 通过分子C₁和C₂两种点群的优化结构,获得不依赖于这两种结构的结果 和有关这个手性系统物理图像的丰富信息.对分子拉曼键极化率分析,得出在拉曼弛豫过程中, 电荷主要从外围流向骨架结构.对分子微分键极化率的分析,显示在不对称C原子和与其相联系的H原子 两侧化学键, C-O和C-CH₃的微分键极化率的符号正好相反,意味着这个分子具有相当好的手性 不对称性质.对比对称和反对称的键极化率、微分键极化率,本文得到这样的结论: 对于(特别是键伸缩的)键极化率,(大体上是)对称的大于反对称的; 而对于微分键极化率则是反对称的大于对称的. 关键词： 旋光拉曼 键极化率 微分键极化率 2,3-丁二醇     

Electric polarizability of pions in semirelativistic quark model

The generalized and static polarizabilities of charged pions, which are considered a relativistic system of two pointlike spinor quarks with a linear interaction potential, are calculated. The relationship between static electricity and generalized polarizabilities of pions is studied in the context of this approach.     

High precision calculation of multipolar dynamic polarizabilities and two- and three-body dispersion coefficients of atomic hydrogen

In this paper we investigate a variationally stable procedure for multipolar dynamic polarizabilities calculation as well as the two- and three-body van der Waals coefficients of the hydrogen atom. This approach provides precise, fast convergent values for real and imaginary frequency-dependent 2 ^L -pole dynamic polarizabilities. Highly accurate two- and three-body van der Waals dispersion coefficients are calculated from dynamic polarizabilities at imaginary photon frequencies. The present approach is also precise for higher interaction orders. The results are compared with previous calculations found in the literature.     

Spin polarizabilities and characteristics of spin-1 hadrons related to parity nonconservation in the Duffin–Kemmer–Petiau formalism

Spin polarizabilities of spin-1 particles typical of spin-1/2 hadrons are established within the Duffin–Kemmer–Petiau formalism using the relativistically invariant effective tensor representation of Lagrangians of two-photon interaction with hadrons. New spin polarizabilities of spin-1 particles associated with the presence of tensor polarizabilities are also determined.     

Dipole polarizabilities of plasma-embedded Ps and H ions

We have investigated the effect of weakly coupled hot plasmas on the dipole polarizabilities of positronium negative ion and hydrogen negative ion. The plasma effect is taken care of by employing a screened Coulomb (Yukawa) potential of Debye type, and highly correlated exponential wave functions are used. Dipole polarizabilities for various screening parameters are reported.     

Raman excitation of (+)‐(R)‐methyloxirane and its origin of optical activity via bond polarizabilities

We studied the bond polarizabilities of chiral (+)‐(R)‐methyloxirane from its Raman intensities. The bond polarizabilities provide much information concerning the electronic structure of its nonresonant Raman‐excited virtual state. At the initial moment of Raman excitation by the 514.5 nm laser, the tendency of the excited charges (mapped out by the bond polarizabilities) is to spread to the methine bond near the stereogenic center and its triangular oxirane skeleton. Thereby, the coupling of the electric dipole induced by the excited charges in the methine bond and the magnetic moment vibrationally induced by the electric current in the triangular oxirane skeleton as the molecule vibrates is shown to be the key factor leading to its significant Raman chirality. When the final stage of Raman relaxation is approached, the relative magnitudes of the bond polarizabilities are congruent to the bond electronic densities of the ground state, which are otherwise by the theoretical quantities via the quantum chemical calculation. During Raman relaxation, we found that the polarizabilities of the peripheral C H bonds relax faster than the rest, as indicated by their relaxation characteristic times. Copyright © 2010 John Wiley & Sons, Ltd.     

碱金属原子多极极化率的解析计算及其应用

通过考虑碱金属原子中的价电子在模型势中的运动, 给出了碱金属原子激发态(包括分立谱和连续谱)的波函数, 导出了碱金属原子的多极动态极化率的计算式中所涉及的矩阵元的解析表达式, 实现了碱金属原子多极动态极化率的解析计算. 作为应用, 利用范德瓦尔斯相互作用系数与动态极化率之间的积分关系, 计算了异核基态碱金属原子间的三体相互作用系数, 将计算结果与此前用稳定变分方法得到的结果进行了比较, 结果显示两者是一致的. 此工作为后续研究激发态碱金属原子间的相互作用奠定了基础.     

Optical birefringence and order parameter of three nematogens

Results of the measurement of refractive indices and densities of three nematic liquid crystals at different temperatures are reported. The molecular polarizabilities have been calculated from refractive indices using both the Vuks’ and the Neugebauer’s relations. The orientational order parameters are determined from the polarizability values. The variation of order parameter with temperature for these compounds shows a reasonably good agreement with Maier and Saupe theory except near the clearing points where the experimental values are less than those obtained from the theory. The possible reasons for this have been discussed.     

Atomic polarizabilities and shielding factors

A detailed discussion is given of the methods of calculating atomic polarizabilities and shielding factors and the relationships between them are demonstrated. The formulation of the uncoupled Hartree-Fock approximation is presented and it is shown that the methods are all approximate versions of it. A more accurate procedure, the coupled Hartree-Fock approximation, is described. Comprehensive tables of dipole and quadrupole polarizabilities and of quadrupole shielding factors are included together with an assessment of the probable accuracy.     

The fractional ionic character of alkali and silver halide crystals

The fractional ionic character of alkali and silver halide crystals is defined in terms of the deviations from the additivity rule for polarizabilities of ions. The electronic polarizabilities of ions are calculated using an empirical relationship according to which the electronic polarizability of an ion can be assumed to be directly proportional to the cube of its radius. The calculated ionicities indicate that the alkali halides are nearly or more than 90% ionic and silver halides are much less ionic which is also evident from the Phillips ionicity scale.     

Interferometric determination of the dispersion of vibrational polarizability and the integrated intensities of fundamental bands of 32, 34SF6 and NF3 molecules

The refractivity of gaseous SF₆ and NH₃ in the region of the intense absorption bands of these compounds was measured by two-beam, two-color interferometry using a He-Ne laser and a CO₂ laser tunable throughout its emission lines. Quantitative data on the profiles of the absorption bands of these gases were also obtained by IR Fourier spectroscopy. By using the joint processing of the results of refractometric and spectral measurements on the basis of the Kramers-Krönig formalism, the dispersion dependences of the vibrational polarizabilities of the given molecules were calculated and the integrated intensities of their fundamental vibrational bands were refined. A table of values of total and vibrational polarizabilities at the emission frequencies of the CO₂ laser was compiled.     

PNO-CI and PNO-CEPA studies of electron correlation effects

Dipole moments and static dipole polarizabilities are calculated for neon and the molecules HF, H₂O, NH₃, CH₄ and CO from SCF and correlated wavefunctions.

The construction of appropriate gaussian-type basis sets is discussed and the convergence of the correlation contributions to the polarizability is analysed. The effect of vibrational averaging is also investigated. The polarizabilities as obtained from the coupled electron pair approximation (CEPA) with the most extended basis sets differ from experimental values by less than 1·5 per cent in all cases. The calculated polarizability anisotropies appear to be correct to about 5–15 per cent. The correlation contributions to the polarizabilities are found to vary from 3 to 12 per cent.     

Investigating neutron polarizabilities through Compton scattering on 3He

We examine manifestations of neutron electromagnetic polarizabilities in coherent Compton scattering from the helium-3 nucleus. We calculate gamma3He elastic scattering observables using chiral perturbation theory to next-to-leading order [O(e2Q)]. We find that the unpolarized differential cross section can be used to measure neutron electric and magnetic polarizabilities, while two double-polarization observables are sensitive to different linear combinations of the four neutron spin polarizabilities.     

Ab initio calculations for the absorption spectra and polarizabilities of small sulfur clusters

Absorption spectra for Sn clusters （n=2...8） are calculated using an adiabatic time-dependent density functional formalism within the local density approximation （LDA）. We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA （TDLDA） spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higherorder finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the ＇hard sphere＇ model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations.     

Crystal-field induced dipoles in heteropolar crystals II: Physical significance

The significance of dipole moments induced by crystal fields in heteropolar crystals is discussed with respect to some aspects of solid state physics. Experimental results from structural analyses that provide data on induced dipoles are summarized. The concept of ionic radii is reconsidered, and a new tabulation scheme is proposed in terms of deformed charge distributions. It is shown that spontaneous polarization as well as the pyro- and piezoelectric coefficients are not independent sets of crystallographic constants, but are accounted for by the structural parameters, the ionic polarizabilities and the elastic constants. The dipole concept is extended to statistically induced or random dipoles. They can account for an important part of the binding energy of substitutionally disordered and non-stoichiometric compounds and, therefore, are concluded to stabilize disorder in solids.