Infrared–microwave double resonance and diode laser spectroscopy of the ν2/ν4 bands of SnH4

Abstract

A pure rotational spectrum of SnH4 has been studied in the ν4 state by infared–microwave double resonance with a tunable diode laser. Twenty-seven double resonance signals have been observed for the 11 JJ–JJ type rotational transitions of the 5 Sn isotopic species. An infrared spectrum of the Coriolis-coupled ν2 and ν4 bands has been measured using a diode laser with Doppler-limited resolution. The ground-state scalar constants, B0, D0, and H0, have been determined by taking combination differences in the ‘‘forbidden’’ ν2 band, which borrows intensity through a strong Coriolis interaction. The observed microwave and infrared data have been analyzed simultaneously by including the Coriolis interaction explicitly. More than 20 molecular constants have been determined accurately for the ν2/ν4 dyad of seven major isotopic species.