Infrared diode laser spectroscopy of the CF3 ν3 band

Abstract

The ν3 degenerate C–F stretching vibration–rotation band of the trifluoromethyl radical was observed in the gas phase by infrared diode laser spectroscopy and was analyzed to determine precisely the rotational constants, centrifugal distortion constants, and the band origin. The spectrum was found to be perturbed by the so-called Δl,ΔK=2,2 and 2,-1 interactions, and an analysis of the perturbation yielded the C0 rotational constant which was otherwise difficult to determine. The two r0 structure parameters, the C–F distance and the F–C–F angle, were calculated from the observed B0 and C0 rotational constants to be 1.318±0.002 Å and 110.76±0.4°, respectively, where the errors were entirely due to the uncertainties of B0 and C0. A general quadratic force field was derived using the fundamental frequencies of 12CF3 and 13CF3 and also the ζ3 Coriolis coupling constant obtained by the present work. The observed vibration–rotation constants α3B and α3C were used to estimate two cubic potential constants φ133 and φ233, and two more constants φ333 and φ334 were obtained from the observed q(2,2 interaction) and r(2,-1 interaction) constants.