AIR-BROADENING, N2-BROADENING, AND O2-BROADENING AND SHIFT COEFFICIENTS IN THE NU-3 SPECTRAL REGION OF (CH4)-C-12

Pressure-broadening and pressure-induced shift coefficients have been measured for more than 450 transitions in the nu3 region of (CH4)-C-12 , between 2650 and 3200 cm-1. The results were obtained by analyzing 2 9 room-temperature laboratory absorption spectra recorded with 0.01-cm -1 resolution using the McMath Fourier transform spectrometer of the N ational Solar Observatory (NSO). Absorption cells with path lengths of 5, 25, and 150 cm, sample pressures of 60-550 torr, and CH4 volume mi xing ratios of 0.01 or less in dry air, N2 or O2 were used. The broade ning and shift coefficients were determined using a nonlinear least-sq uares spectrum fitting technique. Absorption lines belonging to nu3, n u2 + nu4, 2nu4(2) and 2nu2(2) bands of (CH4)-C-12 were observed in the spectra. Transitions up to J'' = 17 in the nu3, J'' = 12 in the nu2 nu4, J'' = 9 in the 2nu4(2) and J'' = 4 in the 2nu2(2) bands were inc luded in the analysis. Variations of the measured parameters with tetr ahedral symmetry species and rotational quantum numbers of the transit ions involved are discussed. Comparisons of the retrieved parameters i n various bands in both (CH4)-C-12 and (CH4)-C-13 are performed in ord er to determine the extent of vibrational dependence.