Mode selective stereomutation tunnelling in hydrogen peroxide isotopomers

The six-dimensional tunnelling dynamics of H2O2, HOOD, and D2O2 are studied on a recently developed analytical global potential energy hypersurface fo r the electronic ground state of hydrogen peroxide. A new formulation of th e harmonic reaction path Hamiltonian approach gives good agreement with the results of a new fully coupled six-dimensional adiabatic channel approach. The experimentally observed pure torsional spectrum and mode specific tunn elling are well reproduced, as are the few known isotope shifts. Prediction s are made for the torsional tunnelling spectrum of HOOD and D2O2. (C) 1999 Elsevier Science B.V. All rights reserved.