摘要:

Large scale configuration interaction calculations are employed to study the potential energy surfaces of the three lowest lying states in H2S+. The calculated structural data for theX2B1andA2A1states are in very good agreement with previous evidence, but the2B2state is found to exhibit an [S---H2]+structure with large SH bond separations and a very small internuclear angle of 32°. Energies and wavefunctions are calculated for all three vibrational modes in theX2B1andA2A1excited states of H2S+and D2S+and the corresponding Franck-Condon factors for theA2A1-X2B1band are determined; a maximum in absorption intensity is predicted to occur forv′2= 5–6 in H2S+and forv′2= 7–8 in D2S+for theA2A1-X2B1transition, for which the calculatedT0energy of 18 620 cm-1is in excellent agreement with the experimentally determined value of 18 520 cm-1. Extensive comparison is made with the otherAH2systems PH2, NH2and H2O+and trends with respect to geometry, vertical excitation and ionization energies as well as vibrational structure are pointed out; for this purpose the2B2potential energy curve of PH2has also been calculated.

ISSN:0026-8976    

DOI:10.1080/00268978000101671

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Ultrasonic absorption and velocity measurements over the frequency range 1 to 10 MHz at 303 K on mixtures of n-hexane and perfluoro-n-hexane confirm the existence of a rotational isomeric relaxation in the perfluoro-compound, and give evidence of a structural relaxation in the liquid mixtures. This last process occurs at frequencies much higher than those associated with conformational change and its amplitude can be predicted from the excess thermodynamic quantities of mixing.

ISSN:0026-8976    

DOI:10.1080/00268978000101681

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In this paper, the spectral shape of the collision induced scattering is calculated in the dipole-induced-dipole approximation for the Raman symmetric vibrational band of optically isotropic molecules. Comparison is made with Rayleigh results. Experimental data for Rayleigh andv1Raman band of CF4are discussed.

ISSN:0026-8976    

DOI:10.1080/00268978000101691

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A calculation of the differential scattering cross section for molecules is needed to interpret neutron diffraction experiments on molecular gases or liquids. In this and a subsequent paper we improve the accuracy of existing calculations to the level achieved by modern experiments, typically 1 per cent. Some of the older models are reexamined and some difficulties with them are discussed. New models for the double differential cross section are presented and integrated numerically over the energy transfer to give the required cross sections. Some recent formulae for this cross section are criticized, and our results are compared to the predictions of these formulae to confirm that they give incorrect results.

ISSN:0026-8976    

DOI:10.1080/00268978000101701

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In this paper we develop useful expansions for the differential cross section in terms of the frequency moments of Van Hove's scattering function, i.e. the Placzek [1] and Wick [3] series. Using only the density independent terms of these series we compare their predictions with those obtained from the models described in paper I. It is concluded that for nitrogen, deuterium chloride and hydrogen chloride the single molecule interference term is given to high accuracy by our Placzek series, so that no density dependent terms are required. For the self terms of nitrogen, and chloride in the HCl and DCl molecules Placzek's series is satisfactory over the range of angles used in most experiments although Wick's series may be needed for angles near 180°. For the self term of D in DCl Wick's series is good over a moderate range of angles, but a realistic model for the rotational behaviour is needed over a wider range and also for all cases involving H in HCl.

ISSN:0026-8976    

DOI:10.1080/00268978000101711

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The proton hyperfine coupling tensors of the methylene protons in methyl-deuterated copper(II) bis(N,N-diethyldithiocarbamate) in a diamagnetic host crystal of the corresponding nickel complex have been measured by ENDOR spectroscopy. Two intermolecular and all four intramolecular proton coupling tensors could be determined. With the aid of spin densities, obtained from extended Hückel molecular orbital calculations, the anisotropic part of the tensors can be reproduced quantitatively, taking into account all two- and three-centre contributions. Comparison of the transition frequencies which are computed from the theoretical tensors with the experimental transitions enables the tracing of another five tensors which cannot be completely determined experimentally.

ISSN:0026-8976    

DOI:10.1080/00268978000101721

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An RKR based inversion procedure for a symmetric double well potential is developed and tested for a model system giving rise to four doubled energy levels below the barrier maximum. Two phase integral functions are extracted from the eigenvalue spectrum, one of which depends on the potential well and the other on the potential barrier and these two functions are then subjected to conventional RKR manipulation. The model potential is reproduced within a few per cent over most of the energy range and the height of the barrier is determined within one per cent.

ISSN:0026-8976    

DOI:10.1080/00268978000101731

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A method for evaluating the higher order phase integrals involving two, three and four turning points is derived and tested with integrals encountered in the symmetric double well problem. The techniques have the form of gaussian-like integration formulae requiring only values of the integrand on the real axis and a straightforward evaluation of weights. Their development allows calculations based on the higher orderJWKBquantization conditions to be done with virtually the same ease now associated with use of the first order approximation.

ISSN:0026-8976    

DOI:10.1080/00268978000101741

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268978000101751

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The depolarized light scattering intensity and second Kerr virial coefficient for SF6are two to three times the values calculated with the dipole-induced-dipole model for the pair polarizability anisotropy and a Lennard-Jones pair potential. Contrary to earlier suggestions, this discrepancy is not attributable to the distribution of polarizable matter within an SF6molecule, at least within the point-atom-polarizability approximation. However, the calculated thermal average of the square of the polarizability anisotropy for SF6can be doubled by replacing the Lennard-Jones potential with a modified Lennard-Jones potential.

ISSN:0026-8976    

DOI:10.1080/00268978000101761

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor