QUANTUM DYNAMICAL STUDIES FOR PHOTODISSOCIATION OF H2O2 AT 248 AND 266 NM

A new quantum mechanical study on UV photodissociation of H2O2 at 248 and 266 nm using a 2D fit to the Schinke-Staemmler's (SS) potential energy surface (PES) [Chem. Phys. Lett. 145, 486 (1988)] is reported. The rotational distributions of the product OH on both the A and B surfaces are found to be considerably hotter than those obtained in a previous quantum study [J. Chem. Phys. 98, 6276 (1993)] using an empirical PES with a very weak dependence on the torsional angle phi. The new calculation shows that the rotation distributions in both the A and B states are Gaussianlike with a maximum at j = 8 on the A surface and at j = 9 on the B surface at 248 nm. Similar distributions are found at 266 nm, but with the maximum shifting lower by approximately one quanta in both the A and B states. The dissociation preferentially produces OH rotations with a high j1 approximately j2 correlation. These conclusions are in excellent agreement with the classical calculation of Schinke-Staemmler at 193 nm photolysis. Although the j distribution (rotation of OH) is similar on both surfaces, the j12(j12 over arrow pointing right = j1 over arrow pointing right + j2 over arrow pointing right) distribution, which reflects the vector correlation of j1 over arrow pointing right and j2 over arrow pointing right, is quite different on two surfaces. Our calculation shows that the A surface gives rise to more bending excitation than the B surface, reflected by a hotter j12 distribution on the A surface. The A and B state branching ratio of H2O2 is also evaluated at 248 and 266 nm photolysis.