Angular-Momentum-Resolved Rydberg State Population of Argon Ions in Strong Laser Fields

This letter demonstrates an experimental approach to measuring the angular-momentum-resolved population of excited states in laser-produced argon ions. By measuring the spectra of free induction decay emissions corresponding to the resonant transitions between Rydberg states, the relative population of the Rydberg states is obtained with known Einstein 𝐴-coefficients. This study deepens the mechanistic understanding of coherent dynamics in laser-driven ionic excited states, and establishes experimental benchmarks essential for validating and refining advanced quantum kinetic models in strong-field physics.