EXAMINATION OF SOME NEW SINGLET TRANSITIONS IN $Li_{2}$

Abstract

Fluorescence spectra of $^{7}Li_{2}$, and $^{7}Li_{2}$, excited by the ultraviolet lines of Argon and Krypton ion lasers have been examined in the infrared region with a Fourier Transform Spectrometer. The various laser lines excited several $C^{1}\Pi_{u} X^{1}\Sigma_{g}^{-}$ and $2^{1}\Sigma_{u}^{\ast}X^{1}\Sigma_{g}^{-}$ transitions and the resulting fluorescence was assigned to the $2{^{1}}\Sigma_{u}\leftarrow 2{^{1}}\Sigma_{g}, c^{1}\Pi_{u}\leftarrow 1^{1}\Pi_{g}, C^{1}\Pi_{u} - 2^{1}\Sigma_{g}$ and $2^{1}\Sigma_{u}-1^{1}\Pi_{g}$ transitions. None of these transitions have been previously observed and this was the first experimental observation of the $2^{1}\Sigma_{u}$ ``double minimum'' state. The assignment and analysis of the spectra will be presented for both isotopes and the results will be discussed in relation to ab-initio calculations. Several perturbations were observed and their assignment and analysis will be presented.