Diode laser spectroscopy and coupled analysis of the ν2 and ν4 fundamental bands of SiH+3

The gas phase infrared spectra of the ν2 and ν4 fundamentals of SiH+3 have been measured between 730 and 1015 cm−1. The ion was produced in an ac glow discharge in silane and hydrogen mixtures. Vibration-rotation transitions were detected using diode laser velocity modulation spectroscopy. 112 transitions were included in a combined fit of both bands which yielded B0=5.214 51(27) and C0=2.585 20(36) cm−1. The ν2 [838.0669(24) cm−1] and ν4 [938.3969(36) cm−1] bands are coupled by a Coriolis x,y resonance for which ξ24=−3.8339(22) based on a calculated value of ξ4=−0.051 27. Experimental band origins and rotational and quartic distortion parameters are compared with recent ab initio calculations.