Optical–optical double resonance and double resonance multiphoton ionization in 7Li2 produced by single cw dye laser excitation

Abstract

A comparison of fluorescence detection of optical–optical double resonance transitions with ionization detection of double resonance multiphoton ionization signals was made for Li2 vapor. The spectra in both cases were excited by a single broadband (30 GHz) cw dye laser and exhibited identical features. These arise from ‘‘accidental’’ two-photon double resonance transitions via real intermediate states and consist of hundreds of distinct transitions in the region 565–645 nm studied in this work. Analysis and assignment reveal that multiphoton excitations within the singlet manifold of electronic states of Li2 together with intermediate state rotational relaxation can account for the spectra. A table of vibrational and rotational assignments of the more intense features is available which includes a comparison between calculated and observed intensities for the transitions.