Measurements of air broadened width and air induced shift coefficients and line mixing in the ν5 band of 12CH3D

In this study we report the first experimental measurements of air-broadening and air-induced pressure-shift coefficients for approximately 400 transitions in the nu(5)(E) perpendicular band of (CH3D)-C-12 in the spectral region 1276-1600 cm(-1). These results were obtained from analysis of 11 room temperature laboratory absorption spectra recorded at 0.005 cm(-1) resolution with the McMath-Pierce Fourier transform spectrometer located on Kitt Peak National Solar Observatory. A multispectrum non-linear least-squares fitting 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 transitions 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 coefficients 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 somewhat smoothly as a function of the rotational quanta, and this behavior has been modeled to +/- 5% using empirical expressions. The off-diagonal relaxation matrix coefficients, W-ij, in cm(-1) atm(-1) at 296 K which are associated 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 previously determined by us for similar transitions in the nu(6)(E) perpendicular band of (CH3D)-C-12 and with other values reported in the literature. (C) 2000 Elsevier Science Ltd. All rights reserved.