Vibration-rotation effects on the polarizabilities of CH 4 and CD 4 calculated from an ab initio polarizability surface

Author： Raynes W.T. Lazzeretti P. Zanasi R.

ISSN： 1362-3028

Source： Molecular Physics, Vol.64, Iss.6, 1988-08, pp. : 1061-1071

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Abstract

A polarizability surface has been calculated for the methane molecule using a Hartree-Fock wavefunction. Coefficients of the surface are given to second order in terms of both symmetry coordinates and internal coordinates. The polarizability is sensitive to bond stretching and angle bending. The effects of nuclear motion on the polarizabilitles of 12 CH 4 and 12 CD 4 have been calculated from the coefficients of the surface. Some of the second order coefficients are found to be significant in contributing to the nuclear motion corrections. The ? 3 mode is the dominant contributor to the corrections. The temperature dependences of the mean molecular polarizabilities of 12 CH 4 and 12 CD 4 are also calculated. The results suggest that modern methods of measurement could distinguish between the isotopomers CH 4- n D n ( n =0–4) thereby enabling an experimental surface to be obtained.