Measurements of air-broadened and nitrogen-broadened Lorentz width coefficients and pressure shift coefficients in the ν_4 and ν_2 bands of 12CH_4

Air-broadened and N_2-broadened halfwidth and pressure shift coefficients of 294 transitions in the ν_4 and ν_2 bands of 12CH_4 have been measured from laboratory absorption spectra recorded at room temperature with the Fourier transform spectrometer in the McMath solar telescope facility of the National Solar Observatory. Total pressures of up to 551 Torr were employed with absorption paths of 5–150 cm, CH_4 volume mixing ratios of 2.6% or less, and resolutions of 0.005 and 0.01 cm^−1. A nonlinear least-squares spectral fitting technique has been utilized in the analysis of the twenty-five measured spectra. Lines up to J″ = 18 in the ν_4 band and J″ = 15 in the ν_2 band have been analyzed.