Inhomogeneous speed effects on H2 vibrational line profiles in ternary mixtures

Abstract

A study of speed inhomogeneous broadening of the hydrogen vibrational line profiles in the collisional regime for ternary mixtures is reported. The Q(1) line of H2 in H2–Ar–N2, H2–He–Ar, and H2–He–N2 mixtures is investigated by high resolution stimulated Raman spectroscopy for various concentrations and temperatures. A model, successfully used for binary mixtures, is extended to ternary mixtures. An excellent agreement is obtained between theory and experiment for H2–Ar–N2, by using the collisional parameters previously obtained from binary mixtures study. For H2–He–Ar and H2–He–N2, H2–He collisions play a “hardening” effect in the H2 soft speed memory mechanism for H2–Ar or H2–N2. The present experimental results allow us, via the frame of our model, to determine the “hardness” parameter values for H2–He (inaccessible from binary mixtures data) and to get an accurate description of the spectral line shape. This study should be useful for hydrogen coherent anti-Stokes Raman spectroscopy thermometry in H2/air flames at high pressure through its possible extension to the H2–N2–H2O system.