A hydrocarbon trinegative ion

Experimental values for ¹H and ¹⁹F nuclear shielding anisotropies obtained from solid state, nematic phase, and molecular beam measurements are reviewed. Certain discrepancies are pointed out. An anisotropy operator is defined as a sum of two operators corresponding to the Lamb and high frequency terms. Approximations to the high frequency operator are given. Scales of absolute shielding constants are obtained, so that the magnitudes of the anisotropies can be discussed on the basis of non-empirical and semi-empirical calculations, and of the experimental results. The hypothesis due to Ramsey that the potential is constant for a given nucleus in different molecules is used to obtain approximate values for the Lamb term in the nuclear shielding constant.

The distinction between shielding in large and small molecules is stressed. For the fluoromethanes and fluorobenzene the results of CNDO/2 molecular orbital calculations are used for a qualitative discussion of the anisotropies.     

Valency electron molecular orbital calculations

The self-consistent perturbation method used previously with the CNDO/2 approximations is generalized to obtain diamagnetic susceptibilities and nuclear shielding constants, as well as polarizabilities, for N₂, BF, CO and F₂ both with a minimal basis set and with a slightly extended set containing an extra 2p orbital. The importance of origin-dependent terms is pointed out. For quantities that depend on the first-order perturbed molecular orbitals, inclusion of the extra 2p orbitals produces results in better agreement with experiment.     

An atomic diffraction theory of molecular photoionization cross sections

A theory of molecular photoionization cross sections is developed on the basis of locally atomic character of the one-electron final state in the Golden Rule expression for the molecular orbital cross section. Ionization amplitudes from several atomic centres are added and rotationally averaged to produce molecular orbital cross sections displaying a sum of pseudo-atomic cross sections weighted according to the LCAO composition of the orbital and also two-centre products reflecting interference effects. The atomic ionization amplitudes are obtained by use of an atomic central potential constructed by an inversion procedure from the form of the ground state orbital. The theory is of a simple chemical nature but usually of at least semi-quantitative accuracy. In this work we illustrate the nature of the two-centre interference effects in small diatomic molecules (H₂, HF, N₂).     

Spectroscopy of the Ωccb baryon in the hypercentral constituent quark model

We extract the mass spectrum of the triply heavy baryon Ω_ccb using the hypercentral constituent quark model. The first order correction is also added to the potential term of the Hamiltonian. The radial and orbital excited state masses are determined, and the Regge trajectories and magnetic moments for this baryon are also given.     

位移损伤剂量法评估空间GaAs/Ge太阳电池辐照损伤过程

本文针对GaAs/Ge太阳电池,利用位移损伤剂量法研究了其在轨服役条件下的性能退化行为.首先在地面模拟辐照环境中,试验获得了在不同能量的电子和质子辐照下的电池性能随辐照注量的退化行为.基于上述实验结果以及计算获得的带电粒子在电池中的非电离能量损失(NIEL)获得了不同能量电子辐照位移损伤的等效指数n为1.7,电子损伤剂量转化为质子损伤剂量等效系数为5.2,并进一步建立了电池性能随位移损伤剂量的退化方程.利用该方法对国产GaAs/Ge太阳电池在500,22000和36000 km轨道带电粒子辐 关键词： GaAs/Ge太阳电池 辐照损伤 带电粒子 位移损伤剂量     

Calculations of diatomic molecules with the LCTCO method. Doubly excited states of the H2 molecule

Nonempirical calculations of 20 autoionizing states of the H₂ molecule are performed in a two-center orbital basis and for two values of the internuclear distance. Results obtained are compared with other results known from the literature.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 31–34, July, 1986.     

Nuclear magnetic relaxation by spin-rotation interaction.

Spin-rotation interaction constants, c, are calculated from the paramagnetic term of the nuclear magnetic shielding constant, σ _p, using a relationship originally due to Ramsey. Calculated values show excellent agreement with experimental determinations from molecular beam measurements. Since σ _p can be easily estimated from the chemical shift of the nuclear resonance this provides a general method for estimating spin-rotation interaction constants.

Chemical shift anisotropies allow the components c _⊥ and c _‖ of the spin-rotation interaction tensor to be determined. Generally both components have the same sign and are of similar magnitude. The r.m.s. value of the spin-rotation interaction constant, required to calculate nuclear spin-lattice relaxation times, is not expected to differ appreciably from average values obtained from molecular beam measurements or magnetic shielding.

Values for the molecular angular velocity correlation time, τ _sr, calculated directly from nuclear spin-lattice relaxation times are about a factor of four longer than those predicted by the relationship between τ _sr and the re-orientation correlation time, τ _d, as given by Hubbard.     

QED theory of the nuclear magnetic shielding in hydrogenlike ions

The shielding of the nuclear magnetic moment by the bound electron in hydrogenlike ions is calculated ab initio with inclusion of relativistic, nuclear, and quantum electrodynamics (QED) effects. The QED correction is evaluated to all orders in the nuclear binding strength parameter and, independently, to the first order in the expansion in this parameter. The results obtained lay the basis for the high-precision determination of nuclear magnetic dipole moments from measurements of the g factor of hydrogenlike ions.     

Visualization of deficiencies in approximate molecular wave functions: the orbital amplitude difference function for the matrix Hartree-Fock description of the ground state of the boron fluoride molecule

The orbital amplitude difference function is used to assess the quality of Hartree–Fock orbitals obtained by invoking the algebraic approximation for the BF ground-state. Systematic sequences of even-tempered, spherical-harmonic Gaussian-type basis functions are used to generate orbitals for which the corresponding total Hartree–Fock energy approaches the 1 μE _h level of accuracy. Exact orbitals are obtained from finite difference calculations using a grid based on spheroidal coordinates. The finite basis set approximations for the orbital are discretized. The accuracy of the discretization is assessed. For each occupied orbital a discretized representation of the orbital amplitude difference function is generated and analysed.     

Extended perturbation formulae for Jahn-Teller molecules

The effect of the Jahn-Teller interaction on a symmetric top molecule with a threefold axis of symmetry in a ^2S + 1E state has been investigated by perturbation theory. Contributions up to sixth order are included. Explicit formulae for various quantities have been derived on the assumption that there is only one Jahn-Teller active mode of vibration; both linear and quadratic Jahn-Teller interactions are considered. The quantities concerned are (i) the vibronic energy levels, (ii) the orbital quenching factor d_t, (iii) the correction to the A-rotational constant, (iv) the correction to the spin-spin dipolar coupling term, and (v) the correction to the spin-rotation coupling constant ε_aa. Because the perturbation expansion converges slowly, the results are only applicable to molecules subject to a weak Jahn-Teller effect. There are several examples of this type of molecule which have been studied experimentally.     

The first principle study on the electronic structure and spin ordering of the rare earth palladium sulfide, EuPd3S4

We have performed relativistic first-principles full-potential linearized augmented plane wave (FLAPW) calculation for rare earth palladium sulfide EuPd₃S₄ in the ferromagnetic and antiferromagnetic states. The density of 4f electrons of Eu is taken from a local-spin-density approximation self-interaction correction (LSDA-SIC) atomic calculation. EuPd₃S₄ is found to exhibit antiferromagnetic ordering in its ground state. The charge, orbital, magnetic moment and spin ordering are explained with the electronic structure, the orbital-projected density of states and the total energy study. EuPd₃S₄ is found to be stable in the body-centered Type-I antiferromagnetic state, in agreement with experimental results. Different Eu states are found in antiferromagnetic ordering. The magnetic moments of different states obtained through spin-polarized calculation are also in good agreement with experimental results. The phenomena observed are explained by the orbital hybridization of Eu and Pd ions as compared with the free ions.     

多解型重原子法

如果重原子具有高于结构的赝对称性,使用重原子法应获得具有多解形式的轻原子位置,我们引入一个赝结构模型并导出了赝结构衍射结构因子F_M(H)的表达式,给出了校正项|E_P(H)|的估算值。将多解型重原子法应用于一个未知结构,获得了完美的赝结构图象。 关键词：     

X-ray magnetic circular dichroism sum rule correction for the light transition metals

Distinguishable L₂ and L₃ edges and a clear separation into j _3/2 and j _1/2 excitations are necessary for the application of L_2,3 edge X-ray magnetic circular dichroism (XMCD) sum rules, which provide element-specific information about spin and orbital magnetic moments. This separation is present for the heavy transition metals (TM), like Co and Ni, due to their large L_2,3 spin–orbit splitting. However, for the light TM, the 2p spin–orbit splitting is strongly reduced and quantum mechanical mixing of j _3/2 and j _1/2 excitations is present. This mixing reduces the observed XMCD related spin and magnetic dipole term contributions and prevents the direct application of XMCD spin sum rules. A large number of 2p?→?3d absorption spectra have been fitted nearly perfectly by a simple and phenomenological model, which takes into account lifetime effects and provides quantitative information about jj-mixing at the light TMs. On the basis of this mixing coefficient, sum rule correction factors have been determined. The proposed model results in renormalized magnetic projected XMCD spin moments, verified for different compounds of V, Cr, and Mn. A comparison with complementary methods gives consistent results. This or a similar fitting procedure and the estimated correction factors can be used in the future as a light element XMCD spin renormalization technique.     

Through-bond and through-space effects on proton chemical shifts. The magnetic anisotropy effects of freely rotating -XY3 groups upon distant protons

A general expression is presented for calculating the contributions of the magnetically anisotropic X-Y bonds of freely rotating -XY₃ groups to the shielding of protons of a freely rotating methyl group elsewhere in the same molecule. The expression can also be modified to calculate (a) the anisotropy contribution of a freely rotating -XY₃ group to the shielding of a fixed proton and (b) the contribution of a fixed anisotropic X-Y bond to the shielding of a freely rotating methyl group. Application is made to calculate the contribution of magnetic anisotropy changes, when a hydrogen atom is replaced by a methyl group, to the aryl and methyl proton chemical shifts of the methylbenzenes relative to benzene and toluene, respectively. Although the contribution of magnetic anisotropy is not negligible it is insufficient to account for the observed shifts. This conclusion applies also to the acetylenic proton chemical shifts of some methyl derivatives of acetylene. Some comments are made on the values of magnetic anisotropy obtained by the N.M.R. method.     

Self-consistent equations of state for hard body mixtures

The self-consistency (S-C) constraints on the solute chemical potential and equation of state are stated and employed to find corrections to thermodynamic functions in the colloidal limit for the most often used equations of state. It is shown that the S-C approach and Henderson's expression for the contact radial distribution functions yield the same correction term in the case of the Boublik—Mansoori—Carnahan—Starling—Leland (BMCSL) equation of state for hard spheres. For hard sphere (and hard convex body) mixtures a new variant of the equation of state and Helmholtz energy is proposed that fulfils better the self-consistency constraints than the frequently used equations. It is shown that the correction term for Δ_{μ 2} in hard convex body mixtures described by improved scaled particle theory differs from that for BMCSL only by the non-sphericity parameter. For the Kolafa—Boublik and modified scaled particle theory versions the correction terms are more complex.     

Rovibrational states of H+ 3. Part 2: The energy region between 9000 cm−1 and 13000 cm−1 including empirical corrections for the non-adiabatic effects

The first part of this series focused on the calculation of the rovibrational states of H⁺ ₃ in the energy region below 9000 cm^?1, where most of the experimentally determined and assigned term values are located. The theoretically justified empirical correction for the non-adiabatic coupling corrections, which was obtained and tested in that study is extended and applied here in the calculation of the rovibrational states of H⁺ ₃ to term values up to 13000 cm^?1, which is above the barrier to linearity. In particular, predictions are made for the 5v ₂ bands, which are the subject of current experimental investigations, hopefully aiding with our results in the assignment of the spectral lines observed.     

CALCULATION OF THE RELATIVISTIC CORRECTION ENERGIES OF Ne-LIKE IONS WITH ORBITAL POLARIZATION CORRECTION

This paper reports the theoretical calculation of Breit, self-energy, and vacuum polarization corrections in the Ne-like system using multi-configuration Dirac-Fock method with the orbital polarization. The relations of these corrections with the atomic number and the orbital symmetries are shown and the calculated correction energies are compared with other calculated results. Our Breit correction energies are all smaller by 1eV as maximum than the other theoretical Breit correction energies and the differences reveal ystematical relation with atomic number. It is found that the configuration interactions have great effect on Breit corrections while the orbital polarization has much smaller effect on Breit corrections. The self-energy and vacuum polarization obtained by our calculation are much different from that in previous literatures for some transitions.     

Vacuum polarization in a hydrogen-like relativistic atom: g factor of a bound electron

The contribution of vacuum polarization to the g factor of a bound electron is considered for the ground state of a hydrogen-like atom. A final expression for the correction is obtained in terms of generalized hypergeometric functions and represents a function of parameter Zα and the ratio of the mass of the orbital particle (electron or muon) to the mass of a particle in the vacuum loop. Different asymptotic forms of this expression are derived for both common and muon atoms.     

Photoelectron spectroscopy of 9,10-dihaloanthracenes

The photoelectron spectra of anthracene and its 9,10-dichloro- and dibromo-derivatives have been obtained. Analysis of the spectra is based mainly on the shifts in the anthracene molecular orbital ionization energies observed upon substitution. These shifts are interpreted on the basis of a perturbation model comprising short-range and long-range inductive terms and a mesomeric term. The electronic perturbation caused by the halogen atom is observed to depend largely on the unperturbed energy of the halogen np electrons and the charge distribution in the anthracene molecular orbitals. It has been possible to separate out Coulombic interactions and mesomeric interactions which depend on the energy gap between hydrocarbon and substituent orbitals. Although the observations are not conclusive, owing to the fact that only two orbitals have measurable mesomeric shifts, results indicate that α_Cl′, the Coulombic perturbation parameter, may well be negative, in contrast to previous work.