Fluorescence lifetimes of <i>EF</i> 1Σ+<i>g</i>, <i>GK</i> 1Σ+<i>g</i>, <i>H</i> 1Σ+<i>g</i>, <i>I</i> 1Π<i>g</i>, and <i>J</i> 1Δ<i>g</i> states of H2 studied by extreme ultraviolet–visible double resonance excitation

Abstract

Extreme ultraviolet–visible double resonance excitation has been employed to populate the EF 1Σ+g, GK 1Σ+g, H 1Σ+g, I 1Πg, and J 1Δg states of hydrogen molecules in the range between 111 500 and 114 000 cm−1. Tunable coherent extreme ultraviolet radiation prepared H2 in the B 1Σ+u (v=5, J) state. The visible laser radiation subsequently brought H2 to higher gerade states. Term values were determined for the J′=0–4 levels, which confirmed the systematic error of 8.01±0.03 cm−1 in the previous analysis by Dieke. The single rovibronic fluorescence lifetimes were measured under a collision-free condition. The fluorescence lifetimes of the I 1Πg(v′ = 0) and J 1Δg(v′ = 0) states, ∼20 and 25 ns, respectively, were found to depend little on the rotational levels. The EF 1Σ+g, GK 1Σ+g, and H 1Σ+g states, on the other hand, exhibited significant rotational dependence. The nonadiabatic coupling among the upper gerade manifolds explained the observed rotational dependence successfully.