15min:

M. ROTGER, W. RABALLAND, V. BOUDON, M. LOETE, Laboratoire de Physique de l'Uni\-versité de Bourgogne, UMR CNRS 5027, 9, av. Alain Savary, B.P. 47870, F-21078 Dijon Cedex, France; J. BREIDUNG, W. THIEL, Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.

We present a development of the dipole moment and polarizability operators of X₂Y₄ molecules, using a tensorial formalism\footnoteW. Raballand, M. Rotger, V. Boudon and M. Loëte, J. Mol. Spectrosc. 217, 239-248, (2003)^, analogous to the one developed for tetrahedral and octahedral molecules. These operators are involved in the calculation of the intensities of rovibrational transitions as well as in the calculation of the Stark effect. Expressions for the matrix elements are derived. A model for the study of the Stark effect in isolated bands of such molecules is proposed and has been used to predict the Stark spectra of the ₁₂ band of ethylene. Values of the polarizability coefficients have been calculated using ab initio methods.