No abstract

The paper presents high resolution Raman investigations of the Q(1) line of H2 in Ar mixture from low density (Doppler regime) to high density (collisional regime) analyzed with a unique line shape profile. Measurements are performed by stimulated Raman gain spectroscopy between 300 and 1000 K in a wide density range (from 0.2 to 11 amagat). All the observed spectral features are accurately described by a unified model recently proposed by two of the authors. This model accounts for a velocity-memory process, not restricted to the usual hard and soft limits. It also includes correlation between velocity- and phase-changing collisions. An exhaustive analysis of various possible mechanisms on the line shape is achieved. These mechanisms are the Dicke narrowing, the radiator speed dependence of the collisional broadening and shifting parameters, the collisionally induced speed-class exchange and the nonimpact effect. The present test shows the high consistency of the unified model, since it allows one to get a remarkable agreement with all the data by using a unique set of parameters. This model should be useful for optical diagnostics at moderate density, as required for combusting media or atmospheric work.

No abstract

A spectral line shape model accounting for both the collisional confinement narrowing of the Doppler distribution and the inhomogeneous effects due to the radiator speed dependence of the collisional broadening and shifting parameters is proposed. The velocity changes are assumed to be induced as well by hard as soft collisions. Doppler-collision correlations and speed-class exchanges are taken into account. A comparison with the previous models used for the Doppler regime and for the collisional one is done. The present model also applies for the intermediate regime where the two above mechanisms are simultaneously efficient. The spectral line shape characteristics are exemplified through the H2–Ar and C2H2–Xe prototype molecular systems.