A MULTISPECTRUM NONLINEAR LEAST SQUARES FITTING TECHNIQUE APPLIED TO THE SPECTURM OF METHANE
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Date
1993
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The multispectrum nonlinear least squares fitting technique described by Benner $et al.^{1}$ has been applied to air and nitrogen broadened spectra of methane in the 2 to $4 \mu m$ spectral region obtained with the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory. Problems fitting the methane spectra one at a $time^{2}$ have been investigated with the multispectrum fitting approach yielding new information about the lineshape below the resolution of the spectrometer. The list of effects now included in the fitting are: Input Parameters. Each spectrum: Pressure, path length and temperature for each of up to 3 paths; mixing ratio for up to 3 gases for each path; apodization function; maximum path difference of FTS; solid angle of FTS entrance aperture. Each spectral line: Gas and Isotope Solvable Parameters. Each spectrum: Second order polynomial fit to continuum; zero level; resolution; period, phase and amplitude for up to 10 channel spectra; diode laser electronic time constant; FTS phase error, period, phase and amplitude of periodic source variations. Each spectral line: Zero pressure position; intensity; lower state energy; self and foreign gas Lorentz broadening; temperature dependence of self and foreign gas Lorentz broadening; self and foreign gas induced pressure shifts; temperature dependence of self and foreign gas induced pressure shifts (2 models); Doppler width; collisional narrowing; line mixing.
Description
$^{1}$ D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith and D. Atkins, $47^{th}$ Ohio State University International Symposium on Molecular Spectroscopy, ME01, June 15, 1993. $^{2}$ D. C. Benner, V. Malathy Devi, M. A. H. Smith and C. P. Rinsland, JQSRT, in press (1993).
Author Institution: Department of Physics, College of William and Mary; Atmospheric Sciences Division, NASA Langley Research Center
Author Institution: Department of Physics, College of William and Mary; Atmospheric Sciences Division, NASA Langley Research Center