VIBRATION ROTATIONAL INTERACTIONS IN THE STATES UPSILON-2 = 1 AND UPSILON-5 = 1 OF H3(CF)-C-12

The vibration-rotational bands ν2 and ν5 of gaseous fluoromethane H312CF have been measured in the region 1250-1600 cm-1 with resolution 0.0034 cm-1; the 2046 lines that have been assigned include 85 lines of the Δk = ±2 perturbation-allowed transitions to the doubly degenerate vibrational state v5 = 1. A variational approach has been applied to the analysis of both bands which are strongly perturbed by x-y Coriolis interaction and by "2, -1" l-type coupling. Simultaneously with 96 previously reported frequencies of pure rotational transitions in the ground vibrational state and 202 frequencies in the excited vibrational states v2 = 1 and v5 = 1 [Pracna, Papoušek, Belov, Tretyakov, and Sarka, J. Mol. Spectrosc. 146, 120-126 (1991)], the wavenumbers of 2046 vibration-rotational transitions of the bands ν2 and ν5 have been fitted to determine 7 parameters of the ν2 band and 21 parameters of the ν5 band. The ground state parameters A0 = 5.1820107(12) cm-1 and DK0 10-6 = 70.39(15) cm-1 are in excellent agreement with those determined previously [Graner, Mol. Phys. 31, 1833-1843 (1976)]. A standard deviation of 8.0 × 10-4 cm-1 has been obtained in the simultaneous fit of the infrared data and 0.38 MHz of the rotational frequencies of the upper state, but in the ν5 band inexplicable systematic differences up to 0.02 cm-1 between the experimental and calculated wavenumbers remain for certain values of the rotational quantum number K at J > 25. From the analysis of the absolute intensities of lines of the ν2 and ν5 bands, we found that (∂μx ∂q5a)/( ∂μz ∂q2) = +1.75, which indicates a negative perturbation of intensity (ζ2.5ay<0). © 1992.