Global Analysis of the Infrared Spectrum of 13CH4: Lines in the Region 0 to 3200 cm–1

Abstract

We have carried out new measurements of infrared spectra in a wide frequency range for the spherical top molecules 12CH4, 13CH4 and 12CD4 at low (80 K) and at room temperature (298 K). Spectra were recorded at very high resolution (0.0027 cm–1 for spectra in the region around 2900 cm–1, which corresponds to the pentad for 13CH4) using the Zürich prototype Bruker 125 spectrometer (ZP 2001) combined with a low temperature cooling cell and a White-type cell. At low temperature, the Doppler full line width at half maximum was reduced by a factor of 1.91 to 0.0045 cm–1 in the pentad region for 13CH4. We report the global analysis of 13CH4-transitions up to 3200 cm–1 and compare to previous work. In the present work line positions are reproduced with an rms deviation of 0.0004 cm–1. The complex interacting system is analyzed using the effective Hamiltonian approach elaborated in Dijon.