Fluorescence lifetimes of the O1Σg+, P1Σg+, R1Πg, and S1Δg states of H2

The rovibronic structures of gerade excited states of molecular hydrogen have been investigated between 117 000 cm−1 and the second dissociation limit with extreme ultraviolet visible double resonant excitation technique. Several levels have been unambiguously assigned to the v = 0 state of the 4s and 4d Rydberg members 4sσO1Σg+, 4dσP1Σg+, 4dπ R1Πg, and 4dδ S1Δg. The fluorescence lifetimes have been measured under collision free conditions for the first time, revealing that the lifetimes for the O1Σg+(v=0) state, 172.8 and 193.7 ns for J = 0 and 1, respectively, are much longer than those for the 4d Rydberg states. The rotational dependence of the lifetimes for the EF+GK+H1Σg+, I1Πg, and J1Δg states is discussed in terms of the nonadiabatic coupling among the upper gerade manifolds.