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-configura tion, and perturbation methods (CASPT2). The A 2PI excited state was c alculated to have a well depth of 811 cm-1 at an internuclear separati on 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. T hese results are in better agreement with experimental results than we re the previously reported pseudopotential calculations. The compariso n 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.