HIGH-RESOLUTION FTIR STUDY OF THE NU-11 AND 2-NU-11 BANDS OF CF2 = CH2

The Fourier transform infrared spectrum of CF2CH2 recorded in the range 400-4000 cm-1 has been analyzed in the ν11 and 2ν11 regions around 802 and 1611 cm-1, respectively, at a resolution of about 0.0017 cm-1. The fundamental ν11, approximately corresponding to the CH2 wagging mode, gives rise to a c-type band whose rovibrational analysis in the P and R branches led to the assignment of more than 5200 transitions with J ≤ 70 and Ka ≤ 63. For the 2ν11 overtone (a-type band) the investigation could also be extended to the Q branch, and more than 3300 transitions with J ≤ 58 and Ka ≤ 27 have been identified. From a simultaneous analysis of ground state combination differences due to the ν11 and the recently studied ν5 bands, together with available literature data mostly consisting of microwave measurements, a set of ground state parameters up to all the sextic centrifugal distortion constants has been obtained. Using the Watson's A-reduction Hamiltonian in the Ir representation, least-squares fits of the assigned transitions provided reliable sets of molecular constants for both the first and second excited vibrational states of ν11 of CF2CH2. © 1992.