IONIZED VAN-DER-WAALS SYSTEMS - STRUCTURE AND INTERACTIONS

Ions of molecular complexes with internal interactions partly of van d er Waals type differ significantly from their neutral parent species i n binding, structure, and dynamics. Information about such systems is still rather scarce, both experimentally and theoretically. The articl e discusses some aspects of the present knowledge concerning cationic dimers and trimers of the type Rg(n)M(+) with Rg denoting a rare-gas a tom, and M, either a (diatomic) molecule or a rare-gas atom, in compar ison with the neutral counterparts. In some more detail, potential ene rgy surfaces (PESs) for the six lowest electronic states of ArHCl+ are reported, as obtained from multireference CI calculations with an ext ended Gaussian AO basis set. From the PESs, structural, energetical, a nd dynamical features are derived. For the cationic argon trimer Ar-3( +) in the electronic ground state, a detailed analysis of the PES, the mode couplings, and the classical internal dynamics is carried out, l eading to a consistent picture of a floppy molecular aggregate with ra pid energy exchange between internal degrees of freedom and early onse t of classical chaos with increasing energy. (C) 1997 John Wiley & Son s, Inc.