Femtosecond time resolved CARS spectroscopy of H2-N2 mixtures in the Dicke regime: Experiments and modeling of velocity effects

Ha Tran (1) , Frédéric Chaussard (2) , N. Le Cong (2) , B. Lavorel (2) , O. Faucher (2) , Pierre Joubert (3)

1 LPM - Laboratoire de Physique Moléculaire (UMR 6624)
2 ICB - Laboratoire Interdisciplinaire Carnot de Bourgogne
3 UTINAM - Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213)

In this paper, we present measurements and modeling of femtosecond time resolved CARS signal in H2-N2 mixtures at low densities. Three approaches have been used to model the CARS response. The first is the usual sum of Voigt profiles. In the second approach, the speed dependent Voigt profile is used. In the last approach, a new model of the CARS signal is developed which takes into account the velocity changes induced by collisions and the speed dependence of the collisional parameters. The velocity changes are modeled using the Keilson and Storer memory function; the radiator speed dependences of the collisional parameters are determined from their temperature dependences. The results show that the changes of the velocity have important effects for the H2/N2 system at the Dicke density regime.

Domaines: Optique [physics.optics]

Ha Tran, Frédéric Chaussard, N. Le Cong, B. Lavorel, O. Faucher, et al.. Femtosecond time resolved CARS spectroscopy of H2-N2 mixtures in the Dicke regime: Experiments and modeling of velocity effects. The Journal of Chemical Physics, 2009, 131, pp.174310. ⟨10.1063/1.3257640⟩. ⟨hal-00447657⟩