Free-jet laser-induced fluorescence spectroscopy of NbN: Observation of a new 3Î state

•Jet-cooled spectra of NbN in the 20,300-20,800 cm−1 spectral region.•Observation of a new 3Π state.•Regular ordering of spin-orbit components of 3Π state but with asymmetric spacing.•Molecular constants indicate perturbation of the 3Π1 spin component.

We report laser-induced fluorescence spectroscopy of the jet-cooled NbN molecule in the 20,300-20,800 cm−1 region. A new 3Π state with spin-orbit components, Π0±3, 3Π1, and 3Π2 respectively at term energies 20,756.32, 20,900.1 and 21,240.3 cm−1 has been observed. The radiative lifetime and rotational constant data suggest that the 3Π1 spin-orbit component is mixed and is responsible for the asymmetric spin-orbit splitting of the 3Π state.