Photodissociation dynamics of H2O2 at 205 nm producing H atoms has been investigated by measuring laser-induced fluorescence spectra of H. From Doppler profile analyses, the average translational energy release was found to be 150.4 +/- 70.1 kJ/mol with the anisotropy parameter, -0.35 +/- 0.05 for the characteristic perpendicular transition. Potential energy surfaces for the S-0, S-1, and T-1 electronic states along the dissociation coordinates were obtained employing density functional theory calculations at the B3LYP/aug-cc-pVTZ level. The dissociation of H from H2O2 instantaneously takes place along the repulsive part of the triplet surface via rapid intersystem crossing from the initially excited S-1 state. (C) 2013 Elsevier B.V. All rights reserved.