LIF spectroscopy and dissociation dynamics of the SiH2 radical in the Ã1B1 (1,v2,0) state

Laser-induced fluorescence (LIF) excitation spectra of the SiH2Ã (1,0,0) – and à (1,1,0)–X̃ (0,0,0) bands, and dispersed fluorescence (DF) spectra from the à (1,0,0) and (1,1,0) levels were measured in the supersonic-free jet. From the rotational structures of the excitation spectra, the rotational constants in à (1,v2,0), v2=0∼2, were determined. The fluorescence decay profiles of the single ro-vibronic levels were also measured, and the fluorescence lifetimes were determined. Based on the lifetimes, it was found that the predissociation depending on the vibronic level starts between the à (1,4,0) and (1,5,0) levels, and the predissociation depending on the rotational level in the à state is suppressed by the ν1 mode excitation and is promoted by the ν2 mode. The latter one is qualitatively explained by considering a second-order predissociation mechanism and a rotation-vibration constant, αiA.