energy transfer viewed in the time domain by femtosecond CARS
coherent anti-Stokes Raman scattering (fs-CARS) provides a powerful tool
for the investigation of collision-induced line broadening and mixing
effects, e.g. for the validation of rotational energy transfer (RET) models.
Whereas the linewidth determination with frequency resolved CARS is limited
to the pressure range, where line mixing effects are negligible (typically
<0.5 amagat for nitrogen), the time domain CARS signal becomes increasingly
sensitive to the off-diagonal elements of the RET matrix at higher pressure
(see figure below) . The application of fs-CARS has very recently led
to a new scaling law proposed for rotationally inelastic collisions,
angular momentum and energy corrected sudden approximation (AECS) [4,5].
Figure: Simulated CARS transients for N2 at 0.2, 1 and 5 bar neglecting
and including line mixing effects and using the ECS-P
model with the parameters of Ref  are compared to the experimental
 G. Knopp, P. Radi, M. Tulej, T. Gerber and P. Beaud, J. Chem. Phys. ,118 (2003) 8223.
 L. Bonamy, et al., J. Chem. Phys. 89 (1988) 5568.
 P. Beaud and G. Knopp, Chem. Phys. Lett. 371 (2003) 194.
 P. Beaud, T. Gerber, P. Radi, M. Tulej, and G. Knopp, Chem. Phys. Lett., 373 (2003) 251.