High-resolution FTIR study of the ν11 and 2 ν11 bands of CF 2CH 2

Abstract

The Fourier transform infrared spectrum of CF 2CH 2 recorded in the range 400–4000 cm −1 has been analyzed in the ν 11 and 2 ν 11 regions around 802 and 1611 cm −1, respectively, at a resolution of about 0.0017 cm −1. The fundamental ν 11, approximately corresponding to the CH 2 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 K a ≤ 63. For the 2 ν 11 overtone ( a-type band) the investigation could also be extended to the Q branch, and more than 3300 transitions with J ≤ 58 and K a ≤ 27 have been identified. From a simultaneous analysis of ground state combination differences due to the ν 11 and the recently studied ν 5 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 I r representation, least-squares fits of the assigned transitions provided reliable sets of molecular constants for both the first and second excited vibrational states of ν 11 of CF 2CH 2.