摘要:

We present a unified theory of diatomic molecules which reconciles bound state spectroscopy and atomic scattering theory. The total wave-function is expanded in a complete set of atomic channel states which is entirely equivalent to an expansion in Hund's case (e) electronic-rotational states. An analysis of the coupled radial, that is vibrational, functions places strong constraints on the asymptotic properties of the molecular wave-functions. These are presented in terms of the reactanceKand scatteringSmatrices of atomic scattering theory which offers a uniform treatment for open channels (inelastic scattering and continuum spectroscopy), closed channels (bound state spectroscopy) and mixtures of both (predissociation). The normalization of the total wavefunction is derived and related to the asymptotic boundary conditions both for continuum and bound states.

ISSN:0026-8976    

DOI:10.1080/00268978000103711

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An exact theory of diatomic molecules must be consistent with atomic scattering theory. In general scattering wavefunctions cannotbe factored into electronic-rotational and radial terms. Yet the starting point of most diatomic analysis is the Born-Oppenheimer approximation (BOA) whichfactorsthe total molecule wavefunction into an electronic-rotational function and a radial or vibrational function which yields the Franck-Condon principle. This is a severe approximation which is at best valid for small amplitude vibrations, may be expected to fail near dissociation limits and is completely invalid in the dissociation continuum.

ISSN:0026-8976    

DOI:10.1080/00268978000103721

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The molecular dynamical evolution from hertzian frequencies to the far infrared (THz) is reported for various kinds of rotator phase environment. The zero to THz frequency spectral profiles are analysed in terms of itinerant libration and developments on this theme. The systems analysed are (i) the plastic rotator phase of t-butyl chloride and solid solutions of this solute in tetramethylsilane; (ii) these results are compared with those from a spectral study in the range up to THz frequencies of t-butyl chloride in vitreous decalin solvent; (iii) single crystalline pentachloronitrobenzene and a pressed disc thereof. This solid is representative of a class of rotator phases where orientational disorder is gradually frozen in at low temperatures, unlike the plastic rotators; (iv) solid solutions of dipolar solute molecules in non-dipolar rotator phase benzene and tetramethylsilane. This is an attempt at evaluating the electrodynamics of dipole-dipole interaction.

ISSN:0026-8976    

DOI:10.1080/00268978000103731

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A heuristic model for pseudospherical molecules is proposed. The model interaction consists of a simple Lennard-Jones potential with an added intermolecular torque which depends on the relative ‘surface velocity’ of colliding particles. Certain unphysical features of the related rough hard sphere model can be avoided in a natural way. Mean squared forces and mean squared torques may be calculated directly from the Lennard-Jones pair correlation function. Results of molecular dynamics calculations on 108-particle rough Lennard-Jones systems are presented.

ISSN:0026-8976    

DOI:10.1080/00268978000103741

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Coupled Hartree-Fock calculations on the susceptibilitiesXand magnetic shielding constants σ are reported for the title molecules. Very large gaussian basis sets have been used in order to come sufficiently close to the Hartree-Fock limit. The basis set dependence ofXand σ is discussed. In addition the applicability of two methods (maximum ofX[20] and closure relations [21, 22]) for the prediction of the best gauge origins is investigated.

ISSN:0026-8976    

DOI:10.1080/00268978000103751

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Coupled-Hartree-Fock calculations of susceptibilities and magnetic shielding constants have been performed for the second row hydrides shown in the title. Large gaussian basis sets have been used which give results near the Hartree-Fock limit. If we want to come close to gauge invariance at least one or two moredfunctions are necessary compared to the first tow hydrides. The influence offfunctions has been tested for HCl. χ and σClwere practically unaffected whereas a change of 1 p.p.m. was found for σH. Use of the closure relation for defining a best gauge origin reduces the size of the basis considerably.

ISSN:0026-8976    

DOI:10.1080/00268978000103761

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

High temperature photoelectron spectroscopy has been used to study the group IV elements, germanium and tin. Bands associated with ionization from the outermostporbital have been observed from the ground state as well as the two lowest states of these elements. Relativistic configuration interaction calculations have been used to calculate experimental band intensities and, from these calculations, the excitation temperature is estimated as 1600±200 K for tin and 2000±200 K for germanium.

ISSN:0026-8976    

DOI:10.1080/00268978000103771

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Pseudo-spectral dipole oscillator strength distributions (DOSDs) are reported for ground state C2H6, C3H8and normal-C4H10, C5H12, C6H14, C7H16and C8H18. The pseudo DOSDs, which are a discrete representation of original recommended continuous DOSDs, can be used to evaluate the dipole properties of the alkanes in a very efficient and economical way without loss of accuracy. The pseudo DOSDs, together with a previous pseudo DOSD for CH4, are used to evaluate the orientation averaged dipole-dipole dispersion energy coefficient, C6(A, B), the corresponding relativistic coefficient,W4(A, B), and the triple-dipole dispersion energy coefficients,C9(A, B, C), for all pairs and triple of molecules taken fromCnH2n+2,n= 1(1)8. The results are used to make self consistent tests of various semiempirical formulae for C6,W4and C9.

ISSN:0026-8976    

DOI:10.1080/00268978000103781

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A variation perturbation method is presented for the direct calculation of intermolecular interaction energies. The theory is based on valence bond ideas but avoids the full evaluation of the matrix elements by expansion in powers of interchange, a procedure which is valid for small overlap between the systems. The participating excited states are regarded as polarized pseudo-states and are determined by optimizing the long-range multipole-multipole part of the interaction energy. The validity of these ideas is illustrated by a calculation of the He-He interaction. A remarkable simplification is pointed out, in which the interaction energy is given almost exactly by the sum of the repulsive term, calculated as zero + single interchange, plus the long-range interaction.

ISSN:0026-8976    

DOI:10.1080/00268978000103791

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The microwave spectrum for thietan-2,2,4,4-d4is analysed in six of its lowest puckering states and up toJ= 25. The close lying pairs of states ofvp= 0/1, 2/3 and 4/5 are treated with a vibration-rotation hamiltonian which includes an off-diagonal coupling term invp. Additional corrections to this coupling term in higher powers of the angular momentum operator are derived and their importance for improving the fit of calculated to observed data is tested. The variation of the centrifugal distortion constants withvpfollows the model of Creswell and Mills (1974,J. molec. Spectrosc.,52,392). A value is determined for the derivative with respect to the puckering coordinate of theac-component of the inverse moment of inertia tensor.

ISSN:0026-8976    

DOI:10.1080/00268978000103801

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor