High resolution infrared spectroscopy and global vibrational analysis for the CH3D and CHD3 isotopomers of methane

We report infrared spectra of CH3D and CHD3 in the range 2900 to 9000 cm(-1) measured with the Zurich high resolution Fourier transform infrared (FTIR) interferometer Bruker IFS 125 prototype (ZP 2001) at 80K in a collisional-cooling cell with optical paths ranging from 5 to 10m. In all, 57 new ro-vibrational bands of CH3D and 40 for CHD3 were assigned and analysed. Using a strategy of the direct assignment of the J=0 states of excited vibrational levels, precise experimental values of the band centres with uncertainties in the range of about 0.0001 to 0.0003 cm(-1) were obtained. Including 15 previously known band centres of CH3D and 12 previously known band centres of CHD3, these data were used as the initial information for the determination of the harmonic frequencies, anharmonic coefficients, and vibrational resonance interaction parameters in an effective hamiltonian. A joint set of 64 parameters reproduces the 124 experimental vibrational energies of both molecules up to 6500 cm(-1) with a root mean deviation of d(rms) 0.73 cm(-1). The results are discussed in relation to intramolecular dynamics on a global potential hypersurface of methane, intramolecular vibrational redistribution, and the spectroscopy of the atmospheres of the earth and planetary systems.