15min:

M. ROTGER, V. BOUDON, M. LOETE, Laboratoire de Physique de l'Université de Bourgogne -- CNRS UMR 5027, 9 Av. A. Savary, BP 47 870, F-21078 DIJON Cedex, FRANCE.

The techniques of symmetry-adapted tensorial formalism and of vibrational extrapolation developed since many years have proved their efficiency for the spectroscopy of spherical-top molecules (CH₄, SF₆, ...). We have recently extended these methods to the case of ``distorted spherical-tops'', i.e.\/ XY₄ or XY₆ type molecules for which one or two of the Y ligands has been substituted by another atom. To do this, we start from the O(3)\supset T_d or O(3)\supset O_h formalism and perform a reorientation into the subgroup C_2v or C_4v.

We have first considered the case of XY₅Z (C_4v) molecules^,. This model has been used to perform the analysis of the ₁/ ₈ dyad of SF₅³⁵Cl A set of programs for spectrum calculations and fits using these methods has been developed and is made freely available through the World Wide Web. We also plan to use these programs for the spectroscopy of SF₅Br or IOF₅, for instance.

We have also undertaken the study of XY₂Z₂ (C_2v) molecules in the aim of studying the quasi spherical-top SO₂F₂. Our model has already been used to perform the analysis of the ground state of this molecule. These results have been compared to those of the usual asymmetric-top approach. We now intend to use this formalism to treat the strongly interacting pentad of this species.