Theoretical investigation of the lower bend-stretch states of the Cl-H2 anion complex and its isotopomers

Coupled-cluster [CCSD(T)] calculations of the potential energy surface of the Cl- H-2 complex were carried out, subsequently averaged over the vibrational motion of the H-2 moiety and then fitted. The lower bend-stretch levels of the anion complex were then determined, for the H-2 molecule in its ground and first excited vibrational levels. The resulting rotational constants agree with earlier experimental values, almost to within the experimental precision. The predicted dissociation energies are 5-8% larger than the experimentally derived values. The bend-stretch wave function of the lowest state of the Cl- oD(2) complex encompasses a considerably larger range of bending motion than in the complexes with oH(2) and pD(2). (C) 2003 American Institute of Physics.