The far infrared pure rotational spectrum and the Coriolis coupling between <i>v</i> ₃ and <i>v</i> ₈ in CH³⁵ClF₂

Abstract

The FIR rotational spectrum of gaseous CH35ClF2 (chlorodifluoromethane, CFC22) is analysed improving vibrational ground state parameters for J up to 80. A new set of rotational and centrifugal distortion constants is given for the C-Cl stretching fundamental v 4. The Coriolis coupling between the two C-F stretching fundamentals v 3 and v 8 is investigated. An effective coupling constant ξ a = 0·38 ± 0·03 cm-1(ξ a 3,8 = 0·56 ± 0·04) was obtained from a rotational analysis of the high resolution FTIR room temperature spectrum (apodized experimental bandwidth: 0·005 cm-1). A ratio of 2 : 1 was estimated for the squares of the vibrational transition moments for the fundamentals v 3 and v 8. A fortran program for simulations and least squares refinements of asymmetric top spectra is described, which allows for the inclusion of any kind of rovibrational coupling between several vibrational states.