VIBRATIONAL OVERTONE SPECTROSCOPY OF THE 4(1)-BAND OF CHF3

The spectra of the 4(1) CH stretch-bend overtone band of (CHF3)-C-12 a nd (CHF3)-C-13 have been obtained at room temperature by intracavity l aser absorption spectroscopy of a CHF, sample with natural isotopic ab undances. The two bands display a resolved and mostly unperturbed J ro tational structure. At the present resolution of 0.02 cm(-1) (half-wid th), the P and R branch J clumps have well resolved Lorentzian profile s with full-widths fluctuating between 0.06 and 0.15 cm(-1), and an av erage value that agrees well with previous estimates. As pressure broa dening was negligible, these are homogeneous linewidths given by intra molecular energy redistribution. The linewidth fluctuations are consis tent with a two-step purely anharmonic coupling of the transition uppe r state to a dense rovibrational bath.