Computer Measurement of Line Strengths with Application to the Methane Spectrum

Computer-aided measurement of absorption line strengths from high resolution spectra greatly improves the accuracies to which relative line strengths can be determined. This article describes a computer program written for interactive use on a Prime minicomputer to fit simultaneously absorption line positions, strengths, linewidths, and continuum parameters. Application to the methane spectrum indicates that relative line strengths have been measured with accuracies of 2% or better for single isolated absorptions. Line strengths from the Q branches of the ν₄ and ν₁ + ν₄ bands of methane are reported and compared to calculated values given in the 1980 Air Force Geophysical Laboratory (AFGL) Compilation of Molecular Parameters.