ADRIANA PREDOI-CROSS, ANIL V. UNNIKRISHNAN, HENRY HEUNG, University of Lethbridge, Department of Physics, 4401 University Drive, Lethbridge, Alberta, TIK3M4, Canada; LINDA R. BROWN, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109; D. CHRIS BENNER AND V. MALATHY DEVI, Department of Physics, The College of William and Mary, Williamsburg, VA 23187-8795.
This study provides the first experimental measurements of line mixing via the off diagonal relaxation matrix element formalism in air-broadened methane spectra for any vibrational band and the first off diagonal relaxation matrix elements associated with line mixing for pure methane in the 2+ 3 band of 12CH4. A speed-dependent Voigt profile with line mixing is used with a multispectrum nonlinear least squares curve fitting technique. The off diagonal relaxation matrix element coefficients of eighteen pairs of 2+ 3 transitions between 4410 and 4629 cm-1 have been determined. The measured self-line mixing coefficients vary from 0.0019 to 0.0390 cm-1atm-1 at 296 K, and for air line mixing coefficients vary between 0.0005 and 0.0205 cm-1atm-1 at 296 K. The spectral data used in the analysis were recorded at a resolution of 0.01-cm-1 using the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona.