HIGH-RESOLUTION FOURIER-TRANSFORM INFRARED-SPECTRUM OF THE NU(2)/NU(5) FUNDAMENTAL-BAND SYSTEM OF (CH3F)-C-13

The vibration-rotational bands nu(2) and nu(5) of gaseous fluoromethane (CH3F)-C-13 were measured in the region 1200-1700 cm(-1) at an unapodized resolution of 0.0041 cm(-1) using an interferometric spectrometer Bruker IFS 120 HR. Almost 3000 lines were assigned including 381 lines of the Delta k = +/-2 perturbation-allowed transitions to the doubly degenerate vibrational state nu(5) = 1. Combination differences were generated for the ground state from the allowed and ''forbidden'' transitions of the nu(2) and nu(5) bands. They were used in a simultaneous fit with the previously measured frequencies of the ground state rotational transitions and the combination differences generated from the nu(3) band (D. Papousek, Z. Papouskova, Yen-Chu Hsu, P. Pracna, S. Klee, M. Winnewisser, and J. Demaison, J. Mol. Spectrosc. 159, 62-68, 1993) to improve the values of the ground state spectroscopical parameters of (CH3F)-C-13. The upper state parameters were determined by fitting simultaneously the infrared data with the frequencies of the rotational transitions in the nu(2) = 1 and nu(5)= 1 levels (preceding paper), using a variational approach with the constrained values of the ground state parameters. (C) 1994 Academic Press, Inc.