Two-photon resonant multiphoton ionisation spectrum of Na2

Abstract

The production of Na: by laser excitation in the 580-620nm region mainly results from two-photon absorption of the Na, molecules to highly excited gerade state(s) and are subsequently ionised by a third photon. This mechanism, i.e., a two-photon resonance three-photon ionisation process, may account for several recent experimental observations in laser-irradiated sodium vapours. The assignment of the multiphoton ionisa- tion spectrum and the dependence of the yield of Na: on the Na, vapour density and the laser power density are presented.