Dissipation of alignment in CO₂ gas: A comparison between ab initio predictions and experiments

We present comparisons between measurements and ab initio calculations of the dissipation of the nonadiabatic laser-induced alignment in pure CO₂ and CO₂-He gas mixtures. The experiments were made for pressures between 2 and 20 bars at 295 K by using short non-resonant linearly polarized laser pulses for alignment and probe. The calculations are carried, free of any adjusted parameter, using refined intermolecular potentials and a requantized Classical Molecular Dynamics Simulations approach presented previously but not yet confronted to experiments. The results demonstrate that the model accurately reproduces the decays with time of both the transient revivals and “permanent” component of the alignment. The significant differences observed between the behaviors resulting from CO₂-CO₂ and CO₂-He collisions are also well predicted by the model.