Probing light-dressed atoms with electrons

An image of electron scattering signals by xenon atoms in a laser field The axes of energy and scattering angle are represented by white arrows. Electron signals originating from the formation of light-dressed states appear in the regions indicated by red circles. © 2015 Kaoru Yamanouchi.

Researchers at the University of Tokyo have succeeded in the first observation of electron scattering signals showing that atoms form “light-dressed states” as a result of laser-atom interaction. This research will deepen our understanding of the “light-dressed state.”

When atoms or molecules are irradiated with light, the light does not normally affect the characteristics of the material. However, it is known that when atoms strongly interact with light, the atoms form new states in which they are dressed by light. While the existence of such “light-dressed states” was known, no experimental methods existed to monitor temporal variations in electron spatial distributions of atoms in light-dressed states.

On the other hand, a theoretical study predicted 30 years ago that characteristic peak signals would be detectable in angular distributions of electrons scattered by atoms in light-dressing states. Although an experimental demonstration of this prediction had been awaited over the years, no reports have been made because of its experimental difficulty.

Professor Kaoru Yamanouchi, Assistant Professor Reika Kanya, and their coworkers at the Department of Chemistry, Graduate School of Science, the University of Tokyo have succeeded in the experimental demonstration of the prediction for the first time. The group performed an experiment of high-energy electron scattering by xenon atoms interacting with an intense laser field, and observed peak structures in energy and angular distributions of the scattered electrons for the first time, showing the formation of light-dressed states.

Detailed analyses of these peak structures will reveal motion of time-dependent electron density distributions of atoms in light-dressed states. This method will enable us to probe temporal variations in electron density distributions in atoms and molecules in intense laser fields, and to understand detailed mechanisms of subsequent dynamical processes such as photoemission and reaction processes.


Yuya Morimoto, Reika Kanya, and Kaoru Yamanouchi, “Light-Dressing Effect in Laser-Assisted Elastic Electron Scattering by Xe“, Physical Review Letters Online Edition2015/09/16 (Japan time), doi: 10.1103/PhysRevLett.115.123201.
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