Global Frequency and Infrared Intensity Analysis of 12CH4 Lines in the 0 - 4800 cm^-1 Region

A new global analysis of methane lines in the 900-4800 cm^-1 region has been performed thanks to new experimental data for both line positions and intensities. This implies three of the 12 CH 4 polyads, namely the dyad (940-1850 cm^-1 , 2 vibrational levels, 2 sublevels), the pentad (2150-3350 cm^-1 , 5 vibrational levels, 9 sublevels) and the octad (3550-4800 cm^-1 , 8 vibrational levels, 24 sublevels) and some of the associated hot bands. New FTIR spectra of the pentad and octad regions have been recorded with a very high resolution (better than 0.001 cm^-1 instrumental bandwidth, unapodized) at 78 K using the Bruker IFS 125 HR Zrich prototype (ZP2001) spectrometer 1 . New intensity measurements were performed in the whole region at the Kitt Peak National Observatory. We also used previously recorded high-resolution Raman spectra 2. The effective Hamiltonian was expanded up to order 6 for the ground state, 6 for the dyad, 5 for the pentad and 5 for the octad. We obtain global root mean square deviations d RMS for line positions = 1.4 œ 10^-4 cm^-1 for the dyad, 6.0 œ 10^-4 cm^-1 for the pentad and 3.3 œ 10^-3 cm^-1 for the octad. This analysis represents a large improvement over the previous one 3 with d RMS = 0.041 cm^-1 for the octad system.