Potential energy surfaces and the spin-orbit coupling for H₂O₂ photodissociation: The importance of the intersystem crossing for Λ-type polarization of product OH

In order to elucidate the mechanism of H₂O₂ photodissociation, especially the origin of the Λ-type preference of product OH, we calculated the potential energy surfaces containing the singlet and triplet states with MRCI method and the spin-orbit coupling on the basis of the Breit-Pauli Hamiltonian. We discussed the results with considering the electronic character of the parent H₂O₂ and its correlation to the Λ-type components of the fragment OH. Consequently, it is proposed that the intersystem crossing from ùA to ³B exerts the branching ratio of the Λ-type components. The relation of the Λ-component ratio with the product rotation J is consistent with the recent experimental findings of vector correlation.