Laser Induced Spectra of SiN Molecule in Near IR Region

Laser-induced spectra of SiN molecule are recorded in the region of 670–1060？nm using laser-induced spectroscopy technique and about 80 bands are observed. Out of total 80 bands, 49 bands are attributed to F-B system and the rest 27 bands are analyzed into J-D system. The rest 18 bands are unidentified. The molecular constant of the , , and states is determined and reported. 1. Introduction Thirty-five red degraded emission bands of SiN molecule, lying in the region of 380–495？nm, were first observed by Jevons [1]. Mulliken [2] reinvestigated the spectra in 380–530？nm region and observed 53 red degraded bands including the bands reported by Jevons [1] and attributed these bands to B2Σ+-X2Σ+ system of SiN molecule. In addition to B2Σ+-X2Σ+ transition, a new transition C-A2Π was also observed by Mulliken [2] in near Uv-green region. Jenkins and De Laszlo [3], on the basis of rotational analysis of B2Σ+-X2Σ+ transition, concluded that the level of B2Σ+ is perturbed. Schoffield and Broida [4] investigated the chemiluminescence spectra of SiN molecule and observed two new electronic transitions in 518–602 and 554–725？nm regions along with B2Σ+-X2Σ+, and C-A2Π systems. Bredohl et al. [5] reinvestigated the spectra in 310–560？nm region and observed three new electronic transitions D2Π-A2Π, L2Π-A2Π, and K2Π-A2Π along with B2Σ+-X2Σ+ system. Foster [6], on the basis of rotational study of four bands, renamed K2Π-A2Π system reported by Bredohl et al. [5] as B2Σ+-A2 system of SiN molecule and calculated ？cm？1 for A2 state. Foster et al. [7] rotationally analyzed (2,0) band of the A2 -X2Σ+ system along with B2Σ+-X2Σ+, D2Π-A2Π, and L2Π-A2Π systems and improved the molecular constants of A2 and X2Σ+ states. Cai et al. [8] calculated rotational and vibrational constants for X2Σ+and A2Π states of the SiN molecule using complete active space SCF (CASSCF), multireference CI (MRCI), and coupled cluster (CCSD(T)) levels. The potential energy curves of the SiN molecule for the low-lying electronic states were also computed by Cai et al. [9] using internally contracted multireference configuration interaction (CMRCI) level. Laser-induced spectroscopy technique is being widely used in the field of molecular spectroscopy to provide laboratory data of molecules. Fu et al. [10], Bondybey [11], Hopkins et al. [12], and Ojha and Gopal [13, 14] have observed a number of new band systems of different molecules using this technique. Therefore, it was decided to investigate the emission spectra of SiN molecule in near IR region. In the present work, the emission spectra of SiN molecule