New assignments in the 2μm transparency window of the 12CH4 Octad band system

Abstract This paper reports new assignments of rovibrational transitions of 12 CH 4 bands in the range 4600–4887  cm −1 which is usually referred to as a part of the 2 μm methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603 m absorption path length and pressures of 1, 7 and 34 hPa for samples of natural abundance CH 4 provided new measurements of 12 CH 4 lines. Older spectra for 13 CH 4 (90% purity) from JPL with 73 m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to th…