The intensities of methane in the 3-5 mu m region revisited

The analysis of the linestrengths of the infrared spectrum of methane (12 a nd 13) in the 3-5 mu m region has been revisited on the basis of new measur ements from Fourier transform spectra recorded at Kitt Peak under various o ptical densities. A simultaneous fit of these new data with previously repo rted tunable difference-frequency laser data has been done. An effective tr ansition moment model in tensorial form up to the third order of approximat ion within the Pentad scheme has been used. The standard deviations achieve d are very close to the experimental precision: 3 and 1.5%, respectively, f or the two sets of data for the (CH4)-C-12 molecule, representing a substan tial improvement with respect to earlier studies. The integrated bandstreng ths obtained in the present work differ from previously reported values by factors ranging from -5 to +6%. The correction for the v(3), band, the stro ngest band of the Pentad system, is +2% with respect to the study of Hilico et al. [J. C. Hilico, J. P. Champion, S. Toumi, V. G, Tyuterev, and S. A. Tashkun, J. Mot Spectrosc. 168, 455-476 (1994)]. (C) 2000 Academic Press.