Infrared Spectrum of Gaseous CF2 by Rapid Scan Spectroscopy

Gaseous CF2 was produced through flash photolysis of CF2Br2, and its infrared spectrum was recorded using a rapid scan infrared spectrometer (500-μsec scan time). The absorption at 1112 cm−1 was recorded at higher resolution, 1 cm−1, than used earlier and the previously postulated PQR band contour was corroborated. Another absorption near 1224 cm−1 was detected for the first time in the gas-phase spectrum and with sufficient resolution to reveal rotational structure. Several sharp features can be assigned as Q-branch transitions in a perpendicular band of a slightly asymmetric top. This shows unambiguously that this band is due to ν1. Two detailed assignments are almost equally plausible, one placing the band center at 1224 ± 1.5 cm−1 and the other placing it at 1229 ± 1.5 cm−1. Both assignments give A″ − 12(B″ + C″) = 2.62 cm−1 and A′ − 12(B′ + C′) = 2.60 cm−1, in acceptable agreement with the microwave value, 2.56 cm−1. The assignments for the transient absorptions at 1112 ± 1.5 cm−1 and at 1224 (or 1229) ± 1.5 cm−1 as ν3 and ν1, respectively, of CF2 are definitively established. Thus ν1 lies at a higher frequency than ν3, as is also true for NF2 and OF2.