Measurements of air broadening, pressure shifting and off diagonal relaxation matrix coefficients in the nu(3) band of (CH3D)-C-12

A multispectrum nonlinear least-squares fitting technique has been applied to determine Lorentz air-broadening coefficients and air induced pressure-s hift coefficients of (CH3D)-C-12 for the nu(3) fundamental band in the spec tral region between 1154 and 1430 cm(-1). This analysis has utilized 11 abs orption spectra recorded at an unapodized resolution of 0.005 cm(-1) with t he McMath-Pierce Fourier transform spectrometer of the National Solar Obser vatory (NSO) on Kitt Peak. Low pressure spectra (with 1-2.99 Torr of enrich ed (CH3D)-C-12 samples) as well as lean mixtures (approximate to 1%) of (CH 3D)-C-12 in dry air (total pressures of 100-400 Torr) at room temperature h ave been measured to determine the pressure broadening coefficients of more than 360 vs transitions with quantum numbers as high as J " = 17 and K " = 17. The measured air-broadening coefficients range from 0.0155 to 0.0726 c m(-1) atm(-1) at 296 K. The pressure-induced shift coefficients vary from a bout - 0.0086 to + 0.0058 cm(-1) atm(-1) The majority of the shifts are neg ative, and the positive shifts often involve transitions with J " = K ". We ak line mixing effects have also been observed in a few high J lines with K " = 3 and approximate off diagonal relaxation matrix coefficients were det ermined for several A(+)A(-) (A1A2) split components. At low to medium valu es of J, the A(+)A(-) splitting is extremely small, and the two components are practically unresolved. Variations of the measured parameters with the A- and E- symmetry species and the rotational quantum numbers of the transi tions involved are discussed. The present results are compared to the few a vailable experimental values in the literature. (C) 2000 Elsevier Science B .V. All rights reserved.