Fourier transform infrared emission spectroscopy of new systems of NiS

The emission spectrum of NiS has been investigated in the near infrared in the 2000-7500 cm−1 region using a Fourier transform spectrometer. New bands observed in the 3000-5000 cm−1 region have been assigned to a 3Πi-X3Σ− transition analogous to the transition of NiO observed in the near infrared [R.S. Ram and P.F. Bernath, J. Mol. Spectrosc. 155 (1992) 315-325]. The 0-0 band of NiS consists of 3Π0+-X3Σ1- (4399 cm−1), 3Π0−-X3Σ− (4257 cm−1), 3Π1-X3Σ0+- (3938 cm−1), and 3Π2-X3Σ1- (3325 cm−1) sub-bands. To higher wavenumbers, another [Ω = 1] - X3Σ0+- transition has been observed with a 0-0 R head near 5887 cm−1. This transition has been assigned as 1Π-X3Σ0+-, although a 3Π1-X3Σ0+- assignment is also possible. Several vibrational bands belonging to different sub-bands were rotationally analyzed and spectroscopic constants evaluated. Our spectroscopic constants for the ground state agree well with the values reported in the microwave study by Yamamoto et al. [T. Yamamoto, N. Tanimoto, T. Okabayashi, Phys. Chem. Chem. Phys. 9 (2007) 3744-3748].