Theoretical study of ultraviolet induced photodissociation dynamics of sulfuric acid

Photodissociation dynamics of sulfuric acid after excitation to the first and second excited states (S-1 and S-2) were studied by an on-the-fly ab initio molecular dynamics simulations based on the Zhu-Nakamura version of the trajectory surface hopping (ZN-TSH). Forces acting on the nuclear motion were computed on-the-fly by CASSCF method with Dunning's augmented cc-pVDZ basis set. It was newly found that the parent molecule dissociated into two reaction-channels (i) HSO4(1(2)A'') + H(S-2) by S-1-excitation, and (ii) HSO4(2(2)A'') + H(S-2) by S-2-excitation. The direct dissociation dynamics yield products different from the SO2 + 2OH fragments often presented in the literature. Both channels result in the same product and differs only in the electronic state of the HSO4 fragment. The trajectories running on S-2 do not hop with S-0 and a nonadiabatic transition happens at the S-2-S-1 conical intersection located at a longer OH bond-length than the S-1-S-0 intersection producing an electronic excited state (2(2)A'') of HSO4 product. (C) 2015 Elsevier B.V. All rights reserved.