PRECISION LIFETIME MEASUREMENTS OF EXCITED STATES IN $H_{2}$

Abstract

We have measured the lifetimes of three rotational-vibrational levels of triplet n = 3 gerade states in molecular hydrogen to a precision of about 2%. We create an intense beam of metastable $2p c^{3}\Pi_{u}$ levels. From these levels, we populate a specific rotational-vibrational level of an n = 3 electronic state by a resonant laser. After a delay, the remaining population is photoionized by a second laser excitation. By measuring the photoionization yield as a function of the delay between the exciting and photoionizing lasers, we measure the lifetime of the excited level. Our measurements reveal subtle problems both with previous lifetime measurements and with recent theoretical calculations.