Interaction forces and energy transfer dynamics of LiH (1gE+) and helium atoms. I. The ab initio evaluation of the lowest potential energy surface Original Research Article

The weak van der Waals (vdW) forces which preside over the interaction of helium with the LiH molecule in its ground electronic state are evaluated very accurately using a recently developed spin-coupled Valence Bond (VB) approach. The target molecule is initially treated as a rigid rotor (RR) at its equilibrium geometry and the behaviour of the interaction is examined over a wide range of orientations and relative distances for the impinging projectile. The general features of the potential anisotropy are analysed in relation to earlier calculations on the same system and foun found to be rather different, especially in the short-range repulsive region for both directions of He approach along the diatomic bond. The full, vibrational PES is also presented by repeating the calculations for five different values of the molecular bond length.