Cavity ring-down spectroscopy of jet-cooled silane isotopologues in the Si-H stretch overtone region

Absorption spectra of silane in the region of the first overtone of the Si-H stretch vibration have been recorded in a seeded supersonic jet expansion by cavity ring-down spectroscopy as well as in a static gas cell at room temperature by photoacoustic spectroscopy. Spectral simplification due to strong rotational cooling in the jet expansion enables us to clearly resolve and assign the rovibrational transitions of the (2000) and (1100) bands of the three isotopologues 28SiH4, 29SiH4 and 30SiH4 in their natural isotopic abundance. Interconversion between different nuclear spin species of SiH4 is found to be absent during the jet expansion. Isotope shifts for 29SiH4 and 30SiH4 relative to 28SiH4 are measured and found to be suitable for selective vibrational excitation of any of three silane isotopologues by pulsed laser excitation in a jet expansion.