摘要:

Dielectric relaxation measurements and for infra-red spectra relative to the samepara-dimethoxybenzene/tetrachloroethylene solution have been concomitantly analysed with13C N.M.R. (T1and N.O.E.) relaxation data, in order to study the intramolecular dynamics of the methoxy and methyl group internal motions. From a direct comparison between the microscopic dipolar (τμ) and N.M.R. (τCNMR) correlation times, it can be shown that the methoxy group internal rotation significantly contributes to the dielectric relaxation process. A quantitative analysis in terms of a ‘Chemical Relaxation Process’ permitted an estimation of both the kinetic constantkcis→transof the dielectrically ‘active’ cis/trans isomerism of thepara-dimethoxybenzene molecule, and of the jumping rate of the methyl group from any of its three equivalent positions. The methoxy-torsional modes for the deuteratedpara-(CD3O)2ϕ and normal species have been assigned to features respectively observed at 82 and 92 cm-1in the far infra-red spectra of these compounds. Also a speculative assignment of the methyl torsions has been investigated. The coherence of the different results has been carefully discussed.

ISSN:0026-8976    

DOI:10.1080/00268977500102521

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Regular oscillations in the differential cross section (DCS) due to nuclear symmetry are used as a sensitive tool to obtain potential curves from measurements. The method is very sensitive to the presence and height of repulsive barriers in the potentials. The DCS for He (11S)-He(21S) collisions at 63 meV using theA1Σu+andC1Σg+potential curves of Guberman and Goddard are compared with molecular beam experiments of Haberland, Chen and Lee, and a reduction of the calculated barrierheights by 15 per cent is indicated. Calculations at other collision energies suggest that measurements of the DCS as a function of energy are a sensitive way of determining experimentally theA1Σu+andC1Σg+curves of He2.

ISSN:0026-8976    

DOI:10.1080/00268977500102531

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

In this paper we provide a direct comparison (over the same molecular basis) of the Equations of Motion (EOM) method and Configuration Internation (CI) methods, for the calculation of excitation properties of water and methane. We find that when double particle-hole interactions have been included in the EOM method and double excitations in the CI method, the results from the EOM method are in closer agreement with the experimental values than the results from the CI method. Furthermore, we find the EOM method to be more economical and convenient, from a computational point of view, than the corresponding CI method. The results from the EOM method also tend to be less sensitive to the choice of basis set than the results from the usual CI treatment.

ISSN:0026-8976    

DOI:10.1080/00268977500102541

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The dipole moment function of thea3Π state of CO is calculated using the multi-configuration self-consistent-field method of Wahl and Das. Only the dominant valence charge-transfer correlation configurations are mixed with the Hartree-Fock configuration since only the region between the classical turning points of thev= 1 vibrational level is considered. The calculated function does not agree with the shape of the fitted dipole moment function of Wickeet al.Configurations chosen on the basis of the model of optimized valence configurations do not determine an accurate dipole moment function for an open shell system.

ISSN:0026-8976    

DOI:10.1080/00268977500102551

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

We review precision dipole moment measurements for COa3Π and the use of these data to extract the dipole moment function over a limited range of internuclear distance. Some of the subtleties involved in the analysis are discussed.

ISSN:0026-8976    

DOI:10.1080/00268977500102561

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The ground state of the FCO+ion is calculated to be linear withRCO= 1·105 Å andRCF= 1·233 Å. As in HCN and FCN, substitution of H by F changes the sign of the stretch-stretch coupling constant.

ISSN:0026-8976    

DOI:10.1080/00268977500102571

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

An approximate expression for the spin correlation functionLnof a one-dimensional system described by the Hubbard Hamiltonian is derived. The result corrects an apparent error in a recent paper by Misurkin and Ovchinnikov. The approximate and exact functions are compared for then= 0 case.

ISSN:0026-8976    

DOI:10.1080/00268977500102581

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

An analytic description of the effects of saturation on the fast and slow-motion E.S.R. lineshapes is presented. Projection operator methods are used to describe the relaxation of the spin system through interactions with a classical lattice, while the effects of the radiation field are described within a quantized field formalism.

ISSN:0026-8976    

DOI:10.1080/00268977500102591

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Brillouin-scattering measurements are reported for the hexagonal plastic crystal norbornylene. The five independent elastic constants at 296 K are determined from the observed Brillouin shifts to beC11= 4·01 ± 0·08,C33= 4·01 ± 0·08,C12= 3·59 ± 0·18,C13= 3·00 ± 0·32 andC44= 0·91 ± 0·03, in units of 109N m-2. The magnitudes of three of the five independent photoelastic coefficients are also determined from Brillouin peak intensity measurements to be |p12| = 0·31 ± 0·02, |p13| = 0·28 ± 0·02 and |p44| = 0·03 ± 0·005.

ISSN:0026-8976    

DOI:10.1080/00268977500102601

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Rayleigh and Raman-scattering experiments are used to study molecular reorientation in the plastic crystalline and liquid phases of norbornylene. The reorientational correlation times obtained from Raman measurements are shown to be in good agreement with those previously determined from N.M.R. spin relaxation time measurements. The depolarized Rayleigh spectra are found to be consistent with Raman and N.M.R. measurements, but intermolecular contributions producing depolarized Rayleigh light are also found to be important. The intermolecular contribution is shown to follow the predictions of the theoretical treatment of Bucaro and Litovitz for collision-induced depolarized light scattering.

ISSN:0026-8976    

DOI:10.1080/00268977500102611

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor