Predissociation dynamics in the 3pπD(1)Πu (±)υ=3 and 4pσB(″) (1)Σu (+)υ=1 states of H2 revealed by product branching ratios and fragment angular distributions.

The predissociation dynamics of H2+XUV→H2 (*)→H(1s)+H(2s,2p) has been studied by measuring the fragment branching ratios between the H(2s) and H(2p) states and the fragment angular distributions using the XUV (extreme ultraviolet) laser pump and UV(ultraviolet) laser probe method. The fragment angular distributions for the predissociation of the 3pπD(1)Πu (+)υ=3 state show parallel transitions, demonstrating that the main components of the dissociating state have (1)Σu (+) symmetry. The measured fragment branching ratios, H(2s)/(H(2s) + H(2p)), for the transitions R(0), R(1), and P(2) in 3pπD(1)Πu (+)υ=3←X(1)Σg (+)υ(″)=0 are in good agreement with one of the previous theoretical predictions. The predissociations of the 3pπD(1)Πu (-)(υ=3) state arising from the Q(1), Q(2), and Q(3) lines have also been observed. The angular distributions and the state distributions of the excited fragments (all found from the H(2p) state) illustrate that the dissociating states for the Q lines have the expected Πu (-) symmetry. The predissociation dynamics of the transition 4pσB(″1)Σu (+)υ=1←X(1)Σg (+)υ(″)=0 was also studied. Their fragment angular distributions show the expected parallel transitions, and most of the fragments are in the H(2s) states. The Beutler-Fano profiles and the associated spectroscopic parameters for the predissociations have also been obtained by measuring the fragment yield of H(2s, 2p) as a function of excitation photon energies.