Torsion-vibration interactions in overtone excited states of hydrogen peroxide

Abstract

The authors investigated the coupling of torsion and OH overtone vibration in hydrogen peroxide by high level ab initio calculations. Within a Born-Oppenheimer framework, the trans barrier and equilibrium torsional angle were calculated as a function of OH stretch and averaged over Morse local-mode wavefunctions for the nine lowest overtone states. Using MP2 and GVB methods at the highly extended 6-311G(3d,2p) basis set level, they obtain near-quantitative agreement with experiment for the dihedral angle and the observed increase of the trans barrier with OH overtone stretching, based purely on potential energy coupling terms of electronic origin.