Vibrational overtone spectroscopy of the 41 band of CHF3

The spectra of the 41 CH stretch-bend overtone band of 12CHF3 and 13CHF3 have been obtained at room temperature by intracavity laser absorption spectroscopy of a CHF3 sample with natural isotopic abundances. The two bands display a resolved and mostly unperturbed J rotational structure. At the present resolution of 0.02 cm−1 (half-width), and P and R branch J clumps have well resolved Lorentzian profiles with full-widths fluctuating between 0.06 and 0.15 cm−1, and an average value that agrees well with previous estimates. As pressure broadening was negligible, these are homogeneous linewidths given by intramolecular energy redistribution. The linewidth fluctuations are consistent with a two-step purely anharmonic coupling of the transition upper state to a dense rovibrational bath.