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; ³Π_r: T ₀ ≤ 52 513, B( Π₀) = 0.634, A ⋍ +23, ∆G( {1}/{2}) = 589 .