摘要:

Martin's perturbation theory result [2] for the dipole moment of three identical spherical atoms at large separations is shown to simplify: There are two contributions to this three-atom dipole and the strength of each factors into a product of the dipole polarizability of one atom and a two-atom average of dipole and quadrupole matrix elements. The simplified results are used to obtain an improved evaluation of the three-atom dipole of three He atoms, employing extensive pseudo-spectral representations of the dipole and quadrupole excitations.

ISSN:0026-8976    

DOI:10.1080/00268977800100891

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The impact parameter method is applied to high Rydberg atoms for estimating Δn=0 dipole transition cross sections. Values for high-lstates are determined in large part by polarization and relativistic fine-structure contributions to energy levels. Computed cross sections for low-lhelium atoms show good agreement with angular momentum transfer cross sections from electron impact experiments over the range 20<n<80.

ISSN:0026-8976    

DOI:10.1080/00268977800100901

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Quasi-elastic Rayleigh scattering of 14·4 keV photons has been measured on supercooled liquid glycerol at -30°C and 0°C by employing the Mössbauer effect. Total scattered intensity, quasi-elastically scattered intensityIqand energy width ofIq(k, ω) have been determined fork=0·6 to 4·2 Å-1. The molecular motion is modelled as: random-walk diffusional motions for the centre-of-mass translation and for the orientation of independent rigid molecules, plus fast-bounded translational jitter (vibration). The model parameters are evaluated. The temperature dependence of the translational diffusion constant corresponds to an activation energy of 12 kcal/mol. Comparison is made especially with N.M.R. results for rotational motion. The effect of orientational jitter (libration) is considered and its possible influence on nuclear magnetic relaxation is pointed out.

ISSN:0026-8976    

DOI:10.1080/00268977800100911

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Employing a simple trick enables one to extend the set of functions for which the MSA is analytically tractable, and thereby obtain the solution, to within a set of constants, of the MSA for the particularly appropriate model of a molten salt in which the interionic interaction is given by a short-range hard core plus a Born-Mayer (exponential) repulsion together with a longrange Coulomb interaction.

ISSN:0026-8976    

DOI:10.1080/00268977800100921

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Directional Compton profiles and molecular scattering factors for the benzene molecule were calculated by using anab initioSCF-LCAO-MO wavefunction. The relation between these properties and the electron distribution in both momentum and coordinate spaces are discussed. TheJ(0)-surface, i.e. the set of directional Compton profilesJ(q) for |q| = 0, is introduced and shown to be a convenient tool for analysing the electron momentum distribution.

ISSN:0026-8976    

DOI:10.1080/00268977800100931

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

An optical-potential method is developed for the calculation of cross sections for vib-rotational transitions in atom-molecule collisions. In this framework the multi-channel scattering equations are replaced by a pair of coupled equations for each vib-rotational transition. The effect of the large manifold of open rotational channels is introduced through an optical potential in each of the coupled equations. Both a phenomenological (trial function) procedure and a theoretical approximate method for obtaining the optical potentials are given. The method remains computationally feasible even in systems with very many open channels.

ISSN:0026-8976    

DOI:10.1080/00268977800100941

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The optical-potential method (OPM) developed in the previous paper is applied to the calculation of a large manifold of transitions of the typev= 1,j,mj→v′= 0,j′,mjin Li + N2collisions. Trends related to the dependence of the cross section σv,j,mj→v′,j′,mjon the statesj,j′andmjare observed and analysed in terms of the physical effects involved. An information-theoretic model of the cross sections is tested as a means for a simple parametric representation of the results.

ISSN:0026-8976    

DOI:10.1080/00268977800100951

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The vertical ionization potential corresponding to the2Eionic state of ammonia has been calculated on the Hartree-Fock level and by a Green's function method taking account of many-body effects. Additional calculations have been performed on the same level of approximation to obtain the linear coupling constants between the electronic and nuclear motions. The Jahn-Teller hamiltonian has been diagonalized numerically and the full spectrum corresponding to the photoionization of ane-electron has been computed. The position and shape of the corresponding band in the experimental photoelectron spectrum are satisfactorily reproduced. Furthermore, an approximate solution of the Jahn-Teller hamiltonian is presented. The results compare well with those obtained by numerical diagonalization.

ISSN:0026-8976    

DOI:10.1080/00268977800100961

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Exact quantum reaction probabilities have been calculated for the collinear reaction F + H2(v= 0) →FH (v′⩽ 3) + H by a modified numerical version of the State Path Sum method. The potential energy surfaces used are the semiempirical LEPS surfaces No. I and No. V of Muckerman, and one based on theab initioSCF CI surface of Benderet al.In each case, a rotated-Morse cubic-spline representation of the surfaces is used in the calculations. For the Muckerman V surface, the results agree well with those of Schatzet al.For the Muckerman I surface, our results are in fair agreement with the calculations of Wuet al., apart from an energy range where the scattering is sensitive to the number of sectors used to represent the surface. We have also found two new narrow scattering resonances for the Muckerman I surface. Although the three surfaces are quite similar, they give rise to considerably different quantitative scattering results. However, the main qualitative features in the scattering can be correlated in a one-to-one manner for the Muckerman I and V surfaces, and there are also some common features for the Benderet al.surface at low translational energies. At high translational energies the Benderet al.surface gives rise to some qualitatively different features. Comparison of the scattering for the three surfaces suggests that certain regions of anab initiosurface need to be known very accurately if quantitatively meaningful scattering results are to be obtained. These regions include the asymptotic diatomic molecule states, resonance scattering regions (if any) and, at low translational energies, the corner and saddle point regions. It is suggested that potential energy surfaces useful in scattering calculations might be obtained by rescalingab initiosurfaces using additional experimental and theoretical information.

ISSN:0026-8976    

DOI:10.1080/00268977800100971

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Analytic functions have been derived for the potential energy surfaces of the ground states of HCN (HNC) and HSiN(HNSi) using a combination of spectroscopic data andab initiocalculations. The potentials derived give no barrier to the approach of H to CN at any angle, but there is a barrier when H approaches SiN, this being larger at the Si end.

ISSN:0026-8976    

DOI:10.1080/00268977800100981

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor