EXAMINATION OF THE STRUCTURE, A-DOUBLING AND PERTURBATIONS IN THE $1{^{2}}\Pi_{g}$ STATE OF $Li_{2}$
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Date
1990
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Ohio State University
Abstract
Fluorescence in the $C^{2}\Pi_{u} - 1^{2}\Pi_{g} 2^{1}\Sigma_{u}^{\ast} - 1^{2}\Pi_{g}$ and $2^{1}\Sigma_{u}^{\ast} - 2^{1}\Sigma_{g}^{\ast}$ transitions of $^{7}Li_{2}$ and $^{6}Li_{2}$. excited by ultraviolet lines of argon and krypton ion lasers, has been studied in the region $7000 - 12000 cm^{-1}$ using a Fourier Transform spectrometer. The rotational analysis concentrates on $^{6}Li_{2}$. In $C^{2}\Pi_{u} 1^{2}\Pi_{g}$ fluorescence, long progressions, up to $v=34$, are observed in the $1^{2}\Pi_{g}$ state. The Dunham coefficients obtained from the analysis are in good agreement with ab-initio calculations. From the data, an RKR potential curve has been constructed for the $1^{2}\Pi_{g}$ state. The dissociation energy has been calculated by several independent methods giving a 1best value1 of $1422.03 0.05 cm^{-2}$. The A-doubling in both isotopomers is found to be irregular, both with respect to vibration and rotation. The interaction between the $1^{2}\Pi_{g}$ and $2^{1}\Sigma_{g}$ states has been studied in detail and is shown to account for the observed Irregularities. The same interaction also accounts for some very strong perturbations observed in the $1^{2}\Pi_{g}$ and $2^{1}\Sigma_{g}$ states of $2^{1}\Sigma_{u}$ Some of these perturbations show very clear intensity interference effects. From an examination of intensity anomalies, ratios of transition moments of $2^{1}\Sigma_{u} - 1^{2}\Pi_{g}$ and $2^{1}\Sigma_{u} - 2^{1}\Sigma_{g}$ transitions have been determined. Details of the above studies will be presented and the results discussed and compared with ab-inltio predictions.
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$^{1}$ On leave from Physics Department, University of New Brunswick, Box 4400, Fredericton, N.B., Canada, E3B 5A3
Author Institution: Laboratoire de Spectrotrie lonique at Moleculaire, Universite Claude Bernard-Lyon I
Author Institution: Laboratoire de Spectrotrie lonique at Moleculaire, Universite Claude Bernard-Lyon I