The pure rotational spectrum of Difluoroiodomethane, CHF₂I

The pure rotational spectrum of CHF₂I has been recorded for the first time, in a supersonic expansion in the region 1.7-17 GHz, and at room-temperature in the region 302-318 GHz. The observed transitions span the values of J″ from 0 up to 67. Precise rotational and centrifugal distortion constants have been determined. Furthermore, the complete iodine nuclear electric quadrupole coupling tensor, in the inertial and principal axes, has been determined. Quantum chemical calculations have been performed to aid with the analysis. Iodine quadrupole mediated perturbations have resulted in the following observations: (i) several transitions having enhanced intensities and (ii) the observation of several forbidden, ΔJ=±2, transitions. Comparisons in electronic structure are made between the series of molecules CH3-nFnX; n=0,1,2,3 and X = Cl, Br, I.