Spectral shape of nitrogen-broadened methane isolated lines

The room temperature nitrogen-broadened spectra of 9 methane isolated transitions were measured at pressures from 20 mbar to 925 mbar using two different spectrometers: a tunable diode laser spectrometer and a difference-frequency laser spectrometer. These lines, located in the v4, v1+v4, v2+v4 and v3+v4 bands, have rotational quantum numbers varying from 0 to 9. The measured spectra were then fitted one-by-one using the Voigt profile. The obtained values of the Lorentz half-width and its rotational dependence were compared with values in the literature. The non-Voigt effect, characterized by the pressure dependence of the broadening coefficients and the fit residuals, was also quantified. These results will be compared with the calculated ones obtained from molecular dynamic simulations for methane diluted in nitrogen as done previously for HCl in Ar and H2O in N2.