UV absorption of LiO in a supersonic jet

We report the first observation of electronic spectra of a lithium oxide in a supersonic jet. Using laser ablation of lithium in the presence of N2O, a new laser-induced fluorescence excitation spectrum in the 325–355 nm region has been observed. We tentatively assign this spectrum to the C2Π–X2Π transition of LiO. When N2O is added downstream of the nozzle instead of being seeded into the inert carrier gas, the 325–355 nm excitation spectrum disappears and a new excitation spectrum is seen much further to the red. From these findings we deduce that the exothermic reaction Li+N2O → LiO+N2 produces a population inversion in the LiO product, most likely an electronic state population inversion.