Knowledge Bank

We have measured lifetimes of several rotational-vibrational levels of the $3s h3\sigma g,3di3\Pi g$, and $3d j3\Delta g$ electronic states in molecular hydrogen. An intense beam of metastable $2p c3\Pi u$ levels is created by electron bombardment. Downstream, a specific rotational-vibrational level of one of the electronic states (of the triplet n=3 manifold) is populated by a resonant laser and, after a delay, photoionized by a second laser excitation. By measuring the photoionization yield as a function of the delay between the excitation and photoionization lasers, we are able to determine the lifetime of the excited level. We compare our measurements with recent theoretical results.