HIGH-RESOLUTION INFRARED SPECTRUM OF THE ν3+ν8 COMBINATION BAND OF JET-COOLED PROPYNE

Propyne (CH3-C≡CH) is an important molecule in astrophysics and planetary atmospheres, and an important constituent of fuels. Spectroscopic investigation of propyne is also of fundamental interest in intramolecular vibrational redistribution (IVR) dynamics of hydrocarbons. Although extensive spectroscopic studies on this simple organic molecule have been performed, the ν3+ν8 band has not been reported before. In this presentation, the high-resolution infrared spectrum of the ν3+ν8 combination band of propyne is presented.a Continuous-wave cavity ring-down spectroscopy is used to measure this weak infrared band in the 3175 cm−1 region using a supersonic free jet. The rotational analysis of the experimental spectrum results in accurate spectroscopic parameters for the ν3+ν8 combination vibrational state. Severe perturbations are found for K = 3 and 4 rotational levels, and are likely due to near-resonant or non-resonant interactions between the ν3+ν8 and other vibrational states. Moreover, three parallel-transition type subbands are observed and their analysis is presented as well.