Fourier transform spectroscopy of new emission systems of NbN in the visible region

The emission spectrum of NbN has been reinvestigated in the 8000-35 000  cm−1 region using a Fourier transform spectrometer and two groups of new bands were observed. The bands observed in the 18 000-20 000 cm−1 region have been assigned to a new 3Π-X3Δ transition. Three bands with R heads near 19 463.8, 19 659.0 and 19 757.0 cm−1 have been assigned as 0-0 bands of the 3Π2-X3Δ3, 3Π1-X3Δ2 and 3Π0±-X3Δ1 subbands, respectively, of this new transition. Three additional ΔΩ = 0 bands have been observed in the 24 000-26 000  cm−1 region. A 0-0 band with an R head near 25 409.9 cm−1 has been assigned as a ΔΩ = 0 transition having X3Δ2 as its lower state while two additional bands with heads near 25 518.7 and 25 534.8 cm−1 were found to be ΔΩ = 0 bands having X3Δ1 as the common lower state. Two of these three bands are perhaps subbands of a 3Δ-X3Δ transition. Most of the excited levels are affected by perturbations.