PRESSURE DEPENDENCES OF LINE PARAMETERS OF THE 𝝂𝟑 + 𝝂𝟒 R(7)F1 TRANSITION OF METHANE DILUTED IN NITROGEN USING THE HARDAND SOFT-COLLISION MODELS

Abstract

In this work, the affection of the Dicke narrowing effect on the spectral shape of the 𝜈3 + 𝜈4 R(7)F1 transition of methane diluted in nitrogen was studied using the Hard- and the Soft- collision line-shape models. Room-temperature absorption spectra of CH4 broadened by N2 were measured at a wide range of pressure using a difference-frequency laser spectrometer. Measured spectra of the studied transition were then one-by-one fitted with the simple Voigt profile as well as the two line-shape models considered the Dicke narrowing effect at two different assumptions of velocity-changing collisions: hard- and soft- collisions. The obtained results confirmed that using these two models leads to better qualities of fit with respect to the Voigt profile. Pressure-dependences of the line-shape parameters were also observed for the considered transition. The results showed a good agreement with other studies.