Semiclassical calculations of tunneling splitting in hydrogen peroxide and its deuterated isotopomers

Torsional tunneling splittings for the ground and selected vibrationally excited states of HOOH, HOOD, and DOOD are calculated using a semiclassical tunneling approach. The approach incorporates tunneling calculations into quasiclassical trajectory simulations and is thus practical for large systems. Comparisons with the experimental and quantum results show that the mode selectivity and isotope effects are generally reproduced in the semiclassical calculations. The causes for the quantitative discrepancies between the quantum and semiclassical calculations are discussed.