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 for the electronic ground state of hydrogen peroxide. A new formulation of the 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 tunnelling are well reproduced, as are the few known isotope shifts. Predictions are made for the torsional tunnelling spectrum of HOOD and D2O2.