New triplet states of SiO

Two new triplet states of SiO (³Σ^? and ³Π_r) which were recently predicted by ab initio calculations (J. M. Robbe, J. Schamps, H. Lefebvre-Brion, and G. Raseev, J. Mol. Spectrosc.74, 375 (1979)) were observed in emission. Fragmentary rotational analyses were performed for two transitions: ³Σ-b³Π_r and ³Π_r-b³Π_r. The following molecular constants (in cm^?1) were derived for the two new electronic states: ³Σ: T₀ ≤ 53 937, B = 0.619; ${}^3\text{Π}{}_{\mathrm{r}}\text{: T}{}_0\text{≤ 52 513, B(}\text{Π}{}_0\text{) = 0.634, A ? +23,}\text{Δ}\text{G(}\text{1}\text{2}\text{) = 589}$.