Using circular dichroism to control energy transfer in multi-photon ionization

TL;DR

This study demonstrates how circular dichroism influences energy transfer in multi-photon ionization of a chiral, laser-excited lithium atom, revealing potential for ultrafast spin-polarized electron pulse control.

Contribution

It introduces a novel experimental setup using circular dichroism to control energy transfer in multi-photon ionization of a chiral atomic system.

Findings

Strong circular dichroism observed near excitation energy.

Helicity-dependent Autler-Townes splitting affects photoelectron energies.

Potential to generate reversible, spin-polarized electron pulses.

Abstract

Chirality causes symmetry breaks in a large variety of natural phenomena ranging from particle physics to biochemistry. We investigate one of the simplest conceivable chiral systems, a laser-excited, oriented, effective one-electron Li target. Prepared in a polarized p state with |m|=1 in an optical trap, the atoms are exposed to co- and counter-rotating circularly polarized femtosecond laser pulses. For a field frequency near the excitation energy of the oriented initial state, a strong circular dichroism is observed and the photoelectron energies are significantly affected by the helicity-dependent Autler-Townes splitting. Besides its fundamental relevance, this system is suited to create spin-polarized electron pulses with a reversible switch on a femtosecond timescale at an energy resolution of a few meV.