||Observation of ionization enhancement in two-color circularly polarized laser fields
Mancuso, Christopher A. ,
Dorney, Kevin M. ,
Hickstein, Daniel D. ,
Chaloupka, Jan L. ,
Tong, Xiao-Min ,
Ellis, Jennifer L. ,
Kapteyn, Henry C.Murnane, Margaret M.
, p.023402 , 2017-08 , American Physical Society
When atoms are irradiated by two-color circularly polarized laser fields the resulting strong-field processesare dramatically different than when the same atoms are irradiated by a single-color ultrafast laser. For example,electrons can be driven in complex two-dimensional trajectories before rescattering or circularly polarized highharmonics can be generated, which was once thought impossible. Here, we show that two-color circularlypolarized lasers also enable control over the ionization process itself and make a surprising finding: the ionization rate can be enhanced by up to 700% simply by switching the relative helicity of the two-color circularly polarized laser field. This enhancement is experimentally observed in helium, argon, and krypton over a wide range of intensity ratios of the two-color field.We use a combination of advanced quantum and fully classical calculations to explain this ionization enhancement as resulting in part due to the increased density of excited states available for resonance-enhanced ionization in counter-rotating fields compared with co-rotating fields. In the future, this effect could be used to probe the excited state manifold of complex molecules.