Dc. Benner et al., AIR-BROADENING, N2-BROADENING, AND O2-BROADENING AND SHIFT COEFFICIENTS IN THE NU-3 SPECTRAL REGION OF (CH4)-C-12, Journal of quantitative spectroscopy & radiative transfer, 50(1), 1993, pp. 65-89
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.