Predissociation dynamics of D2 + hv→ D(1s1/2) + D(2p1/2,3/2, 2s1/2) revealed by the spin-orbit state resolved fragment branching ratios and angular distributions.

Abstract

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(2p1/2,3/2) atom, a branching ratio measurement is a challenge because of small energy spacing between them. For the D(2p1/2,3/2) fragments from the predissociation of D2 + 14.76 eV → D(1s) + D(2s, 2p1/2,3/2) in the 2pπC1Πu (υ = 19) state, we made such measurements by pumping the D(2s, 2p1/2,3/2) fragments to high-lying Rydberg states that are subsequently ionized by a delayed-pulse electric field. In the 2pπC1Πu (υ = 19) state, the D2 molecule dissociates via both shape and Feshbach resonances correlating to the channels D(1s) + D(2p3/2) and D(1s) + D(2p1/2), respectively. The measured spin-orbit branching ratios, 2p3/2/(2p1/2 + 2p3/2), 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.