Line mixing and speed dependence in CO2 at 6348 cm-1:: Positions, intensities, and air- and self-broadening derived with constrained multispectrum analysis

Intensity and line shape parameters which predict spectral lines with absolute accuracies better than 0.3% have been determined for transitions of the 30012 <- 00001 band of 11012 00 centered near 6348 cm(-1) from 26 high resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath-Pierce Fourier transform spectrometer. To maximize the accuracies of the retrieved parameters, the multispectrum non-linear least squares retrieval technique was modified to adjust the rovibrational constants (G, B, D, etc.) and intensity parameters, including Herman-Wallis terms, rather than retrieving the individual positions and intensities. Speed-dependent Voigt line shapes with line mixing were required to remove systematic errors in the fit residuals. Self- and air-broadening (widths and pressure-induced shifts, speed dependence parartieters) and line mixing (off-diagonal relaxation matrix elements) coefficients were thus obtained in the multispectrum fit. Remaining errors were minimized by fitting the weak 30011 <- 00001 band of (OCO)-O-16-C-13-O-16 as well as the weak hot bands 31112 <- 01101, 32212 <- 02201, 40012 <- 10001, and 40013 <- 10002 of (OCO)-O-16-C-12-O-16 that contribute interfering absorptions in this spectral window. This study presents the most extensive set of measurements to date for self- and airbroadening and self- and air-shift coefficients of a near infrared band of CO2, This is also the first study where line mixing parameters have been experimentally determined for any parallel CO2 band. (c) 2007 Elsevier Inc. All rights reserved.