Using Circular Dichroism to Control Energy Transfer in Multiphoton Ionization

Area of Science:

• Atomic, Molecular, and Optical (AMO) Physics
• Quantum Optics
• Chemical Physics

Background:

• Chirality is a fundamental property causing symmetry breaking in diverse natural phenomena, from particle physics to biochemistry.
• Understanding simple chiral systems is crucial for probing fundamental interactions and developing new technologies.
• Laser-matter interactions offer precise control over atomic and electronic properties.

Purpose of the Study:

• To investigate chirality in a simplified one-electron lithium (Li) system.
• To explore the effects of circularly polarized femtosecond laser pulses on oriented Li atoms.
• To demonstrate the creation of spin-polarized electron pulses with high temporal and energy resolution.

Main Methods:

• Preparation of oriented Li atoms in a polarized p state (|m|=1) within an optical trap.
• Irradiation of the Li target with co- and counterrotating circularly polarized femtosecond laser pulses.
• Measurement of circular dichroism and photoelectron energies.

Main Results:

• Observation of strong circular dichroism when laser frequency is tuned near the excitation energy.
• Significant influence of laser helicity on photoelectron energies due to Autler-Townes splitting.
• Demonstration of helicity-dependent Autler-Townes splitting in a chiral atomic system.

Conclusions:

• The studied Li system serves as a model for fundamental investigations of chirality.
• The observed phenomena enable precise control over electron spin polarization.
• This approach allows for the generation of switchable, spin-polarized electron pulses on femtosecond timescales with millielectronvolt energy resolution.