Photodissociation dynamics of HI and DI at 157 nm

Photodissociation dynamics of HI and DI have been studied at 157 nm using the H atom Rydberg tagging time-of-flight technique. The photofragment translational energy distribution spectra and angular distributions of H/D atom products have been measured. Both the I(2P3/2) and I(2P1/2) products come almost exclusively from a perpendicular transition at 157 nm dissociation process, in agreement with the prediction of LeRoy’s model [R.J. LeRoy, G.T. Kraemer, S. Manzhos, J. Chem. Phys. 117 (2002) 9353]. However, the branching ratios of I∗/I measured in the experiment suggests that weak coupling may take place between the potential energy curves, which is noticeably different from the photodissociation of HI in the UV region. The experimental result in this work also suggests that the repulsive state, which has little contribution to the A-band absorption (33 000–53 000 cm−1), plays a greater role in the dissociation of HI and DI at 157 nm.