Laser-Induced Fluorescence Spectroscopy of the Jet-Cooled SiNSi Radical: Vibrationally Hot Bands of the C ²Δ_u–X ²Π_g Transition

We have generated SiNSi in supersonic free expansions and observed the laser-induced fluorescence (LIF) spectrum in the UV region, and rotational structures of vibrationally hot bands have been analyzed. On the basis of the rotational structure, they are assigned to the C̃ (0110) 2Πg– and C̃ (031,30) μ 2Πg–X̃ (0110) μ 2Σu(−) and C̃ (0110) 2Φg–X̃ (0110) 2Δu vibronic bands of the C̃ 2Δu–X̃ 2Πg electronic transition. Observations of the u vibronic levels in the X̃ 2Πg electronic state and the g levels in the C̃ 2Δu state provide valuable information to analyze the vibronic structure of each electronic state. In addition to the three bands, positions of two hot bands, C̃ (0110) 2Πg–X̃ (0110) κ 2Σu(+) and C̃ (031,30) κ 2Πg–X̃ (0110) μ 2Σu(−), have been identified by adopting results from the vibronic analyses of the X̃ 2Πg and C̃ 2Δu electronic states.