FOURIER TRANSFORM SPECTROSCOPY OF THE $1^{3}\Delta_{g}-b^{3}\Pi_{u}$ TRANSITION IN $^{6}Li_{2},$

Author Institution: Physics Dept., University of New Brunswick; Laboratoire de Spectrometrie, Ionique et Mol\'{e}culaire, Universit\'{e} Claude Bernard, Lyon I, 43 boulevard du 11 Novembre 1918, 69622; Laboratoire de Spectrometrie Ionique et Mol\'{e}culaire, Universit\'{e} Claude Bernard, Lyon I, 43 boulevard du 11 Novembre 1918, 69622The $1^{3}\Delta_{g}-b^{3}\Pi_{u}$ transition of $^{6}Li_{2}$, occurring in the visible region between 16000 - 20000 $cm^{-1}$, has been obtained at high resolution using Fourier Transform Spectrometers. The relaxed emission spectrum was observed via Collisionally Induced Fluorescnce (CIF) following (a) excitation of the $C^{1}\Pi_{u}\leftarrow X^{1}\sum_{g}^{+}$ transition by UV lines of Argon and Krypton lasers, and collisional transfer from $C^{1}\Pi_{u}$ to $1^{3}\Delta_{g}$or (b) excitation of via $F^{1}\sum_{g}^{+}\leftarrow A^{1}\sum_{u}^{+}\leftarrow X^{1}\sum_{g}^{+}$ one colour double resonance using a CW ring dye laser, and transfer from $F^{1}\sum_{g}^{+}$ to $1^{3}\Delta_{g}$. The spectra showed many lines which are broadened and shifted as a result of predissociation of $b^{3}\Pi_{u}$ by the $a^{3}\sum_{u}^{+}$ state and many examples of perturbations of $1^{3}\Delta_{g}$ by $2^{3}\Pi_{g}$. Line widths and shifts and rotational constants are shown to be compatible with ab-initio calculations. Details of these results, analysis of perturbations and examination of possible collisional propensity rules will be discussed