Vm. Devi et al., TEMPERATURE-DEPENDENCE OF LORENTZ AIR-BROADENING AND PRESSURE-SHIFT COEFFICIENTS OF (CH4)-C-12 LINES IN THE 2.3-MU-M SPECTRAL REGION, Journal of quantitative spectroscopy & radiative transfer, 51(3), 1994, pp. 439-465
High-resolution (0.01 cm-1) absorption spectra of lean mixtures of CH4
in dry air were recorded with the McMath-Pierce Fourier transform spe
ctrometer (FTS) of the National Solar Observatory on Kitt Peak at vari
ous temperatures between 24 and -61-degrees-C. The spectra have been a
nalysed to determine the values at room temperature of pressure-broade
ned widths and pressure-induced shifts of more than 740 transitions. T
he temperature dependence of air-broadened widths and pressure-induced
shifts was deduced for approx. 370 transitions in the nu1 + nu4, nu3
+ nu4, and nu2 + nu3 bands of (CH4)-C-12 located between 4118 and 4615
cm-1. These results were obtained by analysing a total of 29 spectra
simultaneously using a multi-spectral non-linear least-squares fitting
technique. This new technique allowed the determination of correlated
spectral line parameters (e.g. intensity and broadening coefficient)
better than the procedure of averaging values obtained by fitting the
spectra individually. This method also provided a direct determination
of the uncertainties in the retrieved parameters due to random errors
. For each band analysed in this study the dependence of the various s
pectral line parameters upon the tetrahedral symmetry species and the
rotational quantum numbers of the transitions is also presented.