A new quantum mechanical study on UV photodissociation of H 2O2 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 Ã and B̃ 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 φ. The new calculation shows that the rotation distributions in both the Ã and B̃ states, are Gaussianlike with a maximum at j=8 on the Ã surface and at j=9 on the B̃ surface at 248 nm. Similar distributions are found at 266 nm, but with the maximum shifting lower by approximately one quanta in both the Ã and B̃ states. The dissociation preferentially produces OH rotations with a high j1∼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(j→ 12 = J→1 + J→2) distribution, which reflects the vector correlation of J→ 1 and j→2, is quite different on two surfaces. Our calculation shows that the Ã surface gives rise to more bending excitation than the B̃ surface, reflected by a hotter j 12 distribution on the Ã surface. The Ã and B̃ state branching ratio of H2O2 is also evaluated at 248 and 266 nm photolysis.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry