The NaLi 1 1Σ+( X ) electronic ground-state dissociation limit

The NaLi 1 1Σ+(X) electronic ground state has been studied by Fourier transform spectroscopy and laser-induced fluorescence up to near the dissociation limit. The fluorescence has been induced by Ar+, Kr+ and dye (DCM and rhodamine 6G) laser lines. Fluorescence spectra have been observed up to v″=43 and accurate molecular constants have been calculated for the electronic ground state after reducing the wave numbers of 6417 assigned lines in a least-squares fit. With the molecular constants an inverted-perturbation-approach potential curve has been calculated. A value for the dissociation energy of De=7105.5±1.0 cm−1 has been obtained by fitting the energy levels with high vibrational quantum numbers to a multipolar expansion in the inverse power of the internuclear distance. The multipolar expansion coefficients C6, C8, and C10 have been obtained, showing a good agreement with theoretical values calculated earlier. In the fluorescence spectrum induced by the 476.5 nm Ar+ laser line, extra fluorescence series have been observed. The possible collisional energy transfer in the 1 1Π(B) electronic state at the origin of these lines is discussed.