Lifetime-measurements of alkali-molecules excited by different laserlines

Absorbing different lines of acw-argon ion laser or a He-Ne-laser the alkali molecules Na₂, K₂, Rb₂ and Cs₂ can be pumped into different rotational-vibrational levels of an excited electronic state. The lifetimes of these states have been measured using the phase shift technique at a modulation frequency of 18 Mc/sec. Because of collisions with the always present alkali atoms the excited molecules may undergo collision-induced transitions to other states and their lifetimes are dependent on the atomic pressure. This dependence was measured and the spontaneous lifetimes were obtained by extrapolation against zero pressure. Different collision processes are discussed which compete with the unperturbed fluorescence.