# THE $B^{2}\Sigma \to A^{2}\Pi$ SYSTEM OF SiN

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 Title: THE $B^{2}\Sigma \to A^{2}\Pi$ SYSTEM OF SiN Creators: Foster, Stephen C. Issue Date: 1984 Publisher: Ohio State University Abstract: Electronic emission from the SiN radical, produced by the addition of $SiCl_{4}$ to active nitrogen, has been known for many years. The spectrum is dominated by a strong $B^{2}\Sigma \to X^{2}\Sigma$ system, but also contains weaker $D^{2}\Pi \to A^{2}\Pi, K^{2}\Sigma \to A^{2}\Pi$ and $L^{2}\Pi \to A^{2}\Pi$ band systems. However, no $B \to A$ or $A \to X$ system has been reported and consequently the locations of the A, D, K and L states with respect to the ground state are unknown. Results will be presented which demonstrate that the weak 440 nm violet degraded bands previously assigned to a $^{\prime\prime}K^{2}\Sigma^{\prime\prime} \to A^{2}\Pi system^{1}$ are part of the $B^{2}\Sigma \to A^{2}\Pi$ system of SiN. The analysis of these bands shows that $T (A^{2}\Pi) = 994.4 cm^{-1}$. This very small $T_{e}$ value places the $A \leftrightarrow X$ system in the mid infrared and explains the lack of observation of this system by photographic techniques. Description: $^{1}$ H. Bredohl, I. Dubois, Y. Houbrechts and M. Singh, Canad. J. Phys. 54, 680, 1976. Author Institution: Herzberg Institute of Astrophysics, National Research Council of Canada URI: http://hdl.handle.net/1811/16704 Other Identifiers: 1984-RC-4