			15min:

TENSORIAL FORMALISM FOR ROVIBRONIC SPECTROSCOPY OF C_3v MOLECULES SPECTROSCOPY OF XY₃Z (C_3v) MOLECULES WITH AN EVEN OR ODD NUMBER OF ELECTRONS: A TENSORIAL FORMALISM ADAPTED TO THE SU(2)øtimes C_I\supset C_v^S\supset C_3v^S GROUP CHAIN.

A. EL HILALI, LISA, CNRS/Universités Paris Est et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil, France; V. BOUDON, Laboratoire interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS--Université de Bourgogne, 9, Avenue Alain Savary, BP 47870, F-21078 Dijon Cedex, France.

In molecular spectroscopy, it is often considered that sophisticated group theoretical and tensorial formalism methods are only really useful for spherical top ( i.e. highly symmetrical) molecules, for which they have proven their high efficiency. Consequently, it is usually admitted that symmetric and asymmetric tops ( i.e. lower symmetry) species should be treated using more ``conventional'' methods. However, some key elements of the formalism developed in our group for tetrahedral or octahedral molecules can be used with great profit even for less symmetrical systems: the ability of performing systematic developments of all rovibrational interactions in case of complex polyads and the so-called ``vibrational extrapolation'' which makes global analyses much easier. Firstly, we present the development of a tensorial formalism adapted to the study of XY₃Z type molecules which possess integer angular momenta ( i.e. in a singlet electronic state) by using the O(3)\supset C_v\supset C_3v chain\footnoteA. El Hilali, V. Boudon and M. Loëte, J. Mol. Spectrosc.\/ , 234, 131--121 (2005).^,\footnoteA. El Hilali, V. Boudon and M. Loëte, J. Mol. Spectrosc.\/ , 234, 176--181 (2005).. We present also the C_3v\textttTDS\footnoteA. El Hilali, Ch. Wenger, V. Boudon and M. Loëte, J. Quant. Spectrosc. Radiat. Transfert.\/ , accepted (2010).(C_3v Top Data System) software for spectrum simulation dedicated to the study of symmetric-top molecules belonging to the C_3v point group. Secondly, we present the development of a tensorial formalism adapted to the study of XY₃Z type open-shell species which possess half-integer angular momenta by using the SU(2)øtimes C_I\supset C_v^S\supset C_3v^S group chain\footnoteA. El Hilali, V. Boudon and M. Loëte, J. Mol. Spectrosc.\/ , 239, 41--50 (2006).^,\footnoteA. El Hilali, V. Boudon and M. Loëte, J. Mol. Spectrosc.\/ , 253, 92--98 (2009)..