Infrared spectra of the Li -(H2)n (n=1-3) cation complexes

Abstract

The Li+ - (H2) n n=1-3 complexes are investigated through infrared spectra recorded in the H-H stretch region (3980-4120 cm-1) and through ab initio calculations at the MP2aug-cc-pVQZ level. The rotationally resolved H-H stretch band of Li+ - H2 is centered at 4053.4 cm-1 [a -108 cm-1 shift from the Q1 (0) transition of H2]. The spectrum exhibits rotational substructure consistent with the complex possessing a T-shaped equilibrium geometry, with the Li+ ion attached to a slightly perturbed H2 molecule. Around 100 rovibrational transitions belonging to parallel Ka =0-0, 1-1, 2-2, and 3-3 subbands are observed. The Ka =0-0 and 1-1 transitions are fitted by a Watson A -reduced Hamiltonian yield..