Global analysis of 13CH4 lines in the 0 - 3200 cm-1 region

We have carried out new measurements of infrared spectra of the spherical top molecules 12CH4, 13CH4 and 12CD4 at low – (80K) and room temperature (298K). Spectra were recorded at very high resolution (0.0027 cm−1 around 2900 cm−1) using the Z¨urich prototype Bruker 125 spectrometer (ZP 2001)3 combined with a low temperature cooling cell. Due to low temperature, the Doppler full width at half maximum (0.0045 cm−1 around 2900 cm−1 at 80K) was reduced by a factor of 1.91. We report the analysis of two low – and six room temperature spectra and present the global analysis of 4000 (2000 newly assigned) 13CH4-transitions from 0 up to 3200 cm−1. The results are compared to previous work. In the present work line positions are reproduced with an rms deviation of 0.0009 cm−1. The complex interacting system is analyzed using an effective Hamiltonian. This tensorial formalism is discussed conceptually as well.