High-resolution Fourier-transform intra-cavity laser absorption study of H 12C 13CH and H 13C 13CH at around 12 600 cm −1: a case of strong anharmonic resonances

Abstract

Fourier-transform intra-cavity laser absorption spectroscopy has been used to record high-resolution vibration–rotation overtone spectra of carbon-13 substituted acetylenes, H 12C 13CH and H 13C 13CH, in the third CH stretching overtone region between 12 500 and 12 730 cm −1. The observed spectra of both species contain only parallel bands for which rovibrational spectroscopic parameters have been determined. Several anharmonic resonances have been identified and rotationally analysed using traditional vibration–rotation theory. Altogether six bands, which include ν 1 + 3 ν 3 and 4 ν 3 for H 12C 13CH and ν 1 + 3 ν 3 for H 13C 13CH, have been observed for both species. Four of the six bands in each molecule are reported for the first time.