A line parameter list for the ν 2 and ν 4 bands of 12CH 4 and 13CH 4, extended to J′ = 25 and its application to planetary atmospheres

Abstract

Line parameters (transition frequencies, line strengths, line widths, ground state energies and quantum identifications) for the ν 2 and ν 4 bands of 12CH 4 and 13CH 4 have been calculated for J'⩽25 using the simultaneous coupled fitting procedure of Gray and Robiette. Molecular constants for the ν 2 band of 13CH 4 were estimated from isotopic shifts from 12CH 4 values. Agreement with laboratory spectra, where available, is always well within 1 cm -1 over the entire spectral range covered by the list. The most serious problem in comparison with laboratory data is the omission of lines belonging to “hot” bands in this spectral region. This list is valuable in remote sensing problems for sorting out lines of trace species from weak methane lines and for determining the atmospheric opacity in relatively transparent spectral regions. Applications of the parameter list are demonstrated for remote sounding of the Jovian atmosphere. The list is available on magnetic tape from the authors.