부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.theochem.2006.08.002 Byline: W. Zrafi (a), B. Oujia (a), H. Berriche (b), F.X. Gadea (c) Keywords: Born-Oppenheimer approximation; Diabatisation; Radial coupling; Adiabatic correction; Vibrational shift Abstract: The evaluation of the first and second derivative of the non adiabatic coupling between the several.sup.1[SIGMA].sup.+ adiabatic states of LiH, RbH and CsH molecules, is considered from accurate diabatic and adiabatic data. Such derivatives of the electronic wave function are determined through a numerical differentiation of the rotational matrix connecting the diabatic and adiabatic representations. The first as well as the second derivative presents many peaks, related to ionic-neutral and neutral-neutral coupling between the.sup.1[SIGMA].sup.+ states. Such radial coupling has been exploited to calculate the first adiabatic correction, which corresponds to the diagonal term of the second derivative divided by the reduced mass, for the ground and some excited states of the three molecules. The second adiabatic correction has been determined using the Virial theorem. The first adiabatic correction was added to the adiabatic potential energy curves to re-determine the corrected spectroscopic constants and vibrational energy levels. The vibrational shift, which is the difference between the corrected and the adiabatic levels, has been calculated for X, A, C and D.sup.1[SIGMA].sup.+ states of the three molecules. A shift of some 10cm.sup.-1 is observed for some vibrational levels showing the breakdown of the Born-Oppenheimer approximation. Author Affiliation: (a) Laboratoire de Physique Quantique, Faculte des Sciences de Monastir, Avenue de l'Environnement 5019, Monastir, Tunisie (b) Laboratoire de Physique et Chimie des Interfaces, Faculte des Sciences de Monastir, Avenue de l'Environnement 5019, Monastir, Tunisie (c) Laboratoire de Physique Quantique, UMR5626 du CNRS Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 4, France Article History: Received 6 July 2006; Accepted 1 August 2006