Ab initio potential energy surface and rotationally inelastic collisions of LiH (X1Σ+) with H.: I.: The ab initio evaluation of the potential energy surface

In this work we present a study of the interaction between the hydrogen atom and the LiH (X(1)Sigma(+)) molecule. The potential energy surface describing this interaction has been calculated very accurately for a fixed distance, that is the equilibrium distance of the LiH molecule and for a wide range of orientations and distances between the hydrogen atom and the center of mass of the LiH target system. The H-LiH system has been reduced to a system of only three electrons, those of valence, by replacing Li+ (Is(2)) by a pseudopotential. A large configuration interaction (CI) has been performed. The potential energy curves in terms of Jacobi coordinates V(r(e) = 3.014 a.u., R, gamma), show the strong anisotropy of interaction potential. We note the presence of a double well for the angles around 11degrees. An analytical fitting of the potential energy surface has been realized in order to produce the long range interaction and to calculate the state-to-state rotational cross sections. (C) 2004 Elsevier B.V. All rights reserved.