The 923-cm−1 band of CF235Cl2 (freon 12), studied by infrared-microwave double resonance

Abstract The constants of the 923-cm −1 band ( ν 6 ) of CF 2 35 Cl 2 were accurately determined by the application of infrared-microwave double resonance using CO 2 and N 2 O lasers. The frequencies of 32 ground-state and 34 ( v 6 = 1) state rotational transitions and 14 infrared transitions were measured. The infrared transition frequencies were generally obtained with an accuracy of ± 20 MHz, but in some cases observation of two-photon Lamb-dips allowed the accuracy to be improved to ± 5 MHz. Many double-resonance signals displayed a predominantly “dispersion-type” lineshape and it has been shown that the phase of the observed signals gives information over the relative disposition of the energy levels involved.