High resolution Fourier transform infrared spectroscopy on CH2DI and CHD2I: evaluation of the ground state constants and analyses of the C-I stretching bands ν3

The high resolution (0.0010cm - 1 ) Fourier transform infrared spectra of the partially deuterated methyl iodide molecules CH 2 DI and CHD 2 I have been recorded and analysed in the v 3 band regions around 510cm - 1 . The fundamental band v 3 is associated with the stretching of the C-I bond and the spectra appear therefore as an asymmetric rotor hybrid a/b-type band and hybrid a/c-type band for CH 2 DI and CHD 2 I, respectively. About 4700 transitions in the case of CH 2 DI and about 3900 transitions in the case of CHD 2 I have been assigned. The ground state rotational constants of CH 2 DI and CHD 2 I have been obtained using the ground state combination differences calculated from the assigned v 3 transitions and 16 microwave transitions from literature. The S reduced Watson's Hamiltonian has been used in the calculations. In addition, the upper state parameters describing the v 3 = 1 vibrational states of these molecules have been determined. The obtained ground state constants as well as the upper state parameters have been compared to the corresponding constants of the symmetric top species CH 3 I and CD 3 I.