AB-INITIO STUDY OF THE GROUND AND 1ST-EXCITED STATE OF LIAR

The intermolecular potentials for the X 2SIGMA and A 2PI states of Li...Ar were studied by a variety of multiconfiguration, single-configuration, and perturbation methods (CASPT2). The A 2PI excited state was calculated to have a well depth of 811 cm-1 at an internuclear separation of 2.59 angstrom, in excellent agreement with the 810 cm-1 derived from experimental data. A smaller well of 77 cm-1 was found for the X 2SIGMA ground state at an intermolecular separation of 4.8 angstrom. These results are in better agreement with experimental results than were the previously reported pseudopotential calculations. The comparison of CI calculations with the CASPT2 results shows that the latter is able to give good results for interacting metal-rare gas systems. (C) 1995 John Wiley & Sons, Inc.