Photoelectric absorption spectra of methane (CH4), methane and hydrogen (H2) mixtures, and ethane (C2H6)

K. A. Dick, Uwe Fink

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34 Scopus citations


Long path absorption spectra of methane have been recorded photoelectrically from 4200 to 10,600 Å. The region to the red of 6200 Å was studied with column abundances varying from approx. 0.001-1 km-amagat at a resolution of several Å. Ethane spectra in the same region were taken for abundances from about 0.1-1 km-amagat. Short scans at higher resolution and higher methane abundance were obtained for the 6800 Å absorption in the hope of discerning structure due to the presumed 5v3 band. The region below 6200 Å was recorded under a few high abundance conditions. It was also scanned with mixtures of methane and hydrogen in an attempt to detect absorption features attributable to simultaneous transitions in H2 and CH4. No such bands were detected under the pressures attained. Visual comparison with spectra of Uranus shows that pure methane explains the absorption features of Uranus quite well and that large laboratory amounts are necessary to match the weak absorptions below 6200 Å. A brief description of the complexity of the levels responsible for the methane transitions is given.

Original languageEnglish (US)
Pages (from-to)433-446
Number of pages14
JournalJournal of Quantitative Spectroscopy and Radiative Transfer
Issue number4
StatePublished - Oct 1977

ASJC Scopus subject areas

  • Radiation
  • Atomic and Molecular Physics, and Optics
  • Spectroscopy


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