On the ”Expanded” Local Mode Approach and Isotopic Effect (CH2D2/CH3D/CHD3) in the Methane Molecule
Résumé
Earlier derived, [1] - [3], for the XY2 (C2v and XY3 (C3v molecules) ”expanded local mode model” is applied to the methane-type, XH4, molecules. On the base of using os specially obtained value of the ambiguity parameter, sin gamma , simple value of all transformation coefficients, l_{N \alpha \lambda}, were obtained for the CH4 molecule. It gave us possibility, on the one hand, 1). to derive simple relations between different spectroscopic parameters (harmonic frequencies, anharmonic parameters and vibrational tetrahedral coefficients, rotational-vibrational and rotational tetrahedral coefficients) of the CH4 molecule, and, on the other hand, 2). on the base of the genegal isotopic substitution theory (see, e.i., [4]) to obtain very simple values of transformation l_{N \alpha \lambda}, coefficients for different deuterated species, CH3D, CH2D2, and CHD3, of the methane molecule. As the final step, numerous isotopic relations between different spectroscopic parameters of the mother, CH4, and deuterated, CH3D, CH2D2, CHD3, species were derived. Comparison of the derived relations with the experimental values of spectroscopic parameters shown more than satisfactory correlation of results. [1]. O. N. Ulenikov, R. N. Tolchenov, and Zhu Qing-Shi, Spectrochim. Acta A 52, 1829 – 1841 (1996). [2]. O. N. Ulenikov, S. N. Yurchenko, and R. N. Tolchenov, Spectrochim. Acta A 53, 329 – 334 (1997). [3]. O. N. Ulenikov, R. N. Tolchenov, and Qing-Shi Zhu, Spectrochim. Acta A 53, 845 – 853 (1997). [4]. A. D. Bykov, Yu. S. Makushkin, and O. N. Ulenikov, J. Molec. Spectrosc. 85, 462 – 479 (1981).