Predissociation dynamics of D + hv→ D(1s) + D(2p, 2s) revealed by the spin-orbit state resolved fragment branching ratios and angular distributions.

For molecular photodissociations, the spin-orbit state resolved fragment branching ratios and angular distributions provide deep insight into the dynamics. For the first excited state of the H(2p) atom, a branching ratio measurement is a challenge because of small energy spacing between them. For the D(2p) fragments from the predissociation of D + 14.76 eV → D(1s) + D(2s, 2p) in the 2pπCΠ (υ = 19) state, we made such measurements by pumping the D(2s, 2p) fragments to high-lying Rydberg states that are subsequently ionized by a delayed-pulse electric field. In the 2pπCΠ (υ = 19) state, the D molecule dissociates via both shape and Feshbach resonances correlating to the channels D(1s) + D(2p) and D(1s) + D(2p), respectively. The measured spin-orbit branching ratios, 2p/(2p + 2p), correspond to the diabatic limit, 2/3, which indicates strong spin-orbit state mixings near the dissociation limits. The spin-orbit state resolved fragment angular distributions also support the diabatic dissociation mechanism and illustrate simultaneous shape and Feshbach resonances for the R(0) transition.