Hg-Ar collisions in a strong laser field: competition between intense field and collisional effects

Abstract

The authors present an investigation of the modification caused by an intense laser field to the rates of mJ changing collisions for Hg perturbed by argon. They have studied experimentally the competition between radiative and collisional coupling between mJ states with a strong laser field tuned to the Hg J=1 to J=1 transition at lambda 435.8 nm. Population is pumped into the strongly dressed manifold from the ground state with a weak UV 'probe' laser detuned slightly from the lambda 253.7 nm intercombination line. The fluorescence observed at lambda 404.7 nm depends critically on whether the excitation proceeds via collisional redistribution or resonance through Stark shifted levels. The authors present data that clearly exhibit the effects of this competition. The data show in particular how one can produce excitation to transient Stark shifted levels in the presence of collisions. This will be critical in future experiments on collisions in strong fields.