Room temperature argon broadened halfwidth and pressure-induced line shift coefficients have been determined for 118 transitions in the ν4 band of 12CH4 from analysis of high resolution laboratory absorption spectra recorded with the McMath Fourier transform spectrometer operated on Kitt Peak by the National Solar Observatory. Transitions up to J″= 12 have been measured using a nonlinear least-squares spectral fitting procedure. The variation of the measured halfwidth coefficients with symmetry type and rotational quantum number is very similar to that measured previously for N2 and air broadening, but the absolute values of the argon broadening coefficients are all smaller. On average, the ratio of the argon broadened halfwidth coefficient to the corresponding N2 broadened halfwidth coefficient is 0.877 ± 0.017 (2σ). More than 95% of the pressure-induced shifts are negative with values ranging from -0.0081 to +0.0055 cm-1 atm-1. The pressure shifts in argon are nearly equal to corresponding values measured previously in N2 and air.
Curtis P. Rinsland, V. Malathy Devi, Mary Ann H. Smith, and D. Chris Benner, "Measurements of argon broadened Lorentz width and pressureinduced line shift coefficients in the ν4 band of 12CH4," Appl. Opt. 28, 2111-2118 (1989)