Measurements of air broadened width and air induced shift coefficients andline mixing in the nu(5) band of (CH3D)-C-12

In this study we report the first experimental measurements of air-broadeni ng and air-induced pressure-shift coefficients for approximately 400 transi tions in the nu(5)(E) perpendicular band of (CH3D)-C-12 in the spectral reg ion 1276-1600 cm(-1). These results were obtained from analysis of 11 room temperature laboratory absorption spectra recorded at 0.005 cm(-1) resoluti on with the McMath-Pierce Fourier transform spectrometer located on Kitt Pe ak National Solar Observatory. A multispectrum non-linear least-squares fit ting algorithm was used in retrieving the results. The measured broadening coefficients vary from to 0.0265 to 0.0735 cm(-1) atm(-1) at 296 K for tran sitions up to J" = 17 and K" = 12, including 12 forbidden lines with Delta K = +/- 2 (5 (O)Q and 7 (S)Q). The corresponding pressure-induced shift coe fficients range from + 0.0003 and - 0.0088 cm(-1) atm(-1) and the majority of these are negative. Subsets of air-broadened width coefficients vary som ewhat smoothly as a function of the rotational quanta, and this behavior ha s been modeled to +/- 5% using empirical expressions. The off-diagonal rela xation matrix coefficients, W-ij, in cm(-1) atm(-1) at 296 K which are asso ciated with line mixing were determined for a few transitions with K" = 3 ( A(+)A(-) splitting) in the PP and PQ sub-bands. The broadening and pressure -shift coefficients obtained from the analysis are compared with values pre viously determined by us for similar transitions in the nu(6)(E) perpendicu lar band of (CH3D)-C-12 and with other values reported in the literature. ( C) 2000 Elsevier Science Ltd. All rights reserved.