Fluorescence of the Na*–N2 collision complex

The fluorescence spectrum of Na(3p) atoms in N2 gas has been measured in the far wings of the Na resonance lines, from 550–790 nm. We observe a broad continuum from 630–790 nm that is independent of N2 pressure and gas temperature, and which agrees with that calculated from the theoretical NaN2 potentials of Habitz if one includes only free collision states of the Na*N2 molecule. We conclude that this continuum is due to an attractive Na(3p)–N2 interaction, but that bound states in this potential well predissociate to Na(3s) and vibrationally excited N2 in much less than the Na* radiative lifetime of ∼16 ns. The intensity on the blue wing of the Na resonance lines decreases rapidly with decreasing wavelength, and shows temperature dependence corresponding to a repulsive Na(3p)–N2 interaction. Good agreement is obtained with a blue-wing spectrum calculated from the X̃ and B̃ states of Habitz.