Testing van der Waals interactions with quantum dynamics : Repulsive anisotropy and well depth in the LiH+He system

Recent calculations on the rigid rotor surface for the LiH–He interaction [B. K. Taylor and R. J. Hinde, J. Chem. Phys. 111, 973 (1999)] surmised that the well depth and anisotropy of the new surface differ substantially from the latest valence bond calculations for the same system [F. A. Gianturco, S. Kumar, S. K. Pathak, M. Raimondi, M. Sironi, J. Gerratt, and D. L. Cooper, Chem. Phys. 215, 227 (1997)]. We examine in detail the performance of both these potential energy surfaces once employed to generate quantum observables which can be compared with experiments. Our computations clearly show that the two surfaces exhibit small differences in their short-range repulsive anisotropy and larger differences in well depths. The latter however cannot be assessed as yet from existing experiments. The different behavior of their wells in supporting van der Waals bound states is also examined and spectroscopic experiments are suggested for detecting possible transitions between such states.