Strongly resonant RABBITT on lithium

TL;DR

This paper investigates how strong resonance in RABBITT processes with lithium significantly alters ionization dynamics, providing new insights into the resonant phase of two-photon transitions in atomic systems.

Contribution

It demonstrates that strong resonance in lithium's RABBITT process affects the entire photoelectron spectrum and reveals the resonant phase, a novel insight into laser-atom interactions.

Findings

Resonant RABBITT modifies the full photoelectron spectrum in lithium.

The study uncovers the resonant phase of two-photon transitions.

Resonance influences ionization dynamics beyond previous observations.

Abstract

The process of reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) can become resonant with a discrete atomic level either in the intermediate or the final continuous states. Experimental observations of the former [Phys. Rev. Lett. 104, 103003 (2010)] or latter [Nat. Commun. 7, 10566 (2016)] cases revealed modification of only those parts of the photoelectron spectrum that overlapped directly with the resonance. In the lithium atom and other members of the alkali metal family, the valence shell $ns\to np$ transition to the intermediate RABBITT state affects the whole photoelectron spectrum in the final state. The strong additional resonant channel modifies entirely the ionization dynamics and opens direct access to the resonant phase of the two-photon transitions which is common for various single and multiple electron ionization processes. Elucidation of this phase has wider implications for strongly resonant laser-matter interaction.