Infrared spectrum and molecular force field of CF2Cl2

Abstract The infrared spectrum of CF 2 Cl 2 has been measured under medium resolution in the range 1600-400 cm −1 . More than 100 bands including fundamental, overtone, combination, and “hot” bands of the three isotopic species CF 2 35 Cl 2 , CF 2 35 Cl 37 Cl, and CF 2 37 Cl 2 have been identified. The band contour studies have enabled the fundamental vibrations to be unambiguously assigned, including the modes ν 3 and ν 7 , the positions of which were previously in doubt. The observed values for CF 2 35 Cl 2 in conjunction with the frequency shift data for CF 2 35 Cl 37 Cl and CF 2 37 Cl 2 have been used in determining a general valence force field, which adequately describes the system investigated. A Fermi resonance interaction between ν 8 and ν 3 + ν 9 levels for the three isotopic species has been interpreted. The corresponding perturbations between those levels obtained by adding ν 2 or ν 5 to both ν 8 and ν 3 + ν 9 have also been found and the related features carefully investigated.