The far infrared pure rotational spectrum and the Coriolis coupling between v₃ and v₈ 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.