Laser-induced fluorescence spectroscopy of the jet-cooled HNCN radical

Abstract

The observation of laser-induced fluorescence spectra of the jet-cooled HNCN free radical is reported. The HNCN free radical was generated by ArF laser photolysis of a mixture of NH₃, C₂N₂ and N₂ in the ratio 1 : 1 : 10 in the first stages of a supersonic free jet expansion. Evidence suggests that the mechanism of formation of HNCN under these conditions is CN + NH₂→ HNCN + H. The lifetime of the excited ²A′ state is found to be 20 ± 5 ns. Molecular constants were obtained by a least-squares fit of the present and previously published data to an effective rotational Hamiltonian. Approximate vibrational intervals in the ground state of the radical were measured for the first time by dispersing the laser-induced fluorescence. The dispersed fluorescence spectra show activity in a bending vibration, assigned from its parallel rotational structure to the δ(HN—C—N) a″ mode. This is interpreted as evidence for a Renner–Teller effect in the radical.