N₂-broadening coefficients in the ν₄ band of ¹²CH₄ at room temperature

Using a diode laser spectrometer, we have studied with a great accuracy the N-broadening coefficients in the ν band of methane. The experiments were performed at room temperature for lines in the P- and R-branches. We have measured 39 lines in the spectral range 1237-1373 cm with J values between 1 and 12. Each line under study was recorded at four different nitrogen pressures, ranging from 20 to 91 mbar. The collisional half-widths were obtained by fitting individually a theoretical profile on the experimental profile of each line at each N-pressure. We fitted the usual Voigt profile, but also the Rautian and Galatry lineshape models which take into account the collisional narrowing due to the molecular confinement (Dicke effect). The Rautian and Galatry fits are always better adjusted on the experimental profiles. For some lines, when the overlapping could not be disregarded, a fit of the blended profiles was performed using the same lineshape models. The collisional broadening coefficients obtained with Galatry and Rautian models are nearly equal and always higher than those derived from Voigt profile. Finally, we compare our results with previous determinations realized for several absorption bands.