FOURIER TRANSFORM SPECTROSCOPY OF $^{7}Li_{2}$: THE $1^{3}\Sigma^{+}_{g}-1^{3}\Sigma^{+}_{u}$ TRANSITION

Fluorescence resulting from excitation of $^{3}Li_{2}$ by the 476.5 nm line of an Argon ion laser has been detected at very high resolution using a Fourier Transform spectrometer at Orsay. A very rich, complex spectrum is obtained in the 8000-10000 cm-1 region. By comparing results of a preliminary rotational analysis with ab-initio calculations, the spectrum has been assigned to the $1^{3}\\Sigma^{+}_{g}-1^{3}\\Sigma^{+}_{u}$ transition, and is the first triplet system of $Li_{2}$ to be observed at high resolution. The results of a global fit to the 31 analyzed bands will be presented and rotational constants, dissociation energies, potential curves and Franck-Condon Factors will be discussed and compared with ab-initio calculations.