Autoionizing Polaritons in Attosecond Atomic Ionization

TL;DR

This study investigates autoionizing polaritons in argon using attosecond transient-absorption spectroscopy, revealing their formation, controllable stabilization against ionization, and underlying interference mechanisms, advancing understanding of light-matter interactions in the continuum.

Contribution

It introduces the first experimental observation and theoretical analysis of autoionizing polaritons, demonstrating optical control and stabilization mechanisms in atomic ionization processes.

Findings

Observation of avoided crossings indicating polariton formation

Controllable stabilization of polaritons against ionization

Agreement with ab initio theory and interference-based stabilization mechanism

Abstract

Light-induced states are commonly observed in the photoionization spectra of laser-dressed atoms. The properties of autoionizing polaritons, entangled states of light and Auger resonances, however, are largely unexplored. We employ attosecond transient-absorption spectroscopy to study the evolution of autoionizing states in argon, dressed by a tunable femtosecond laser pulse. The avoided crossings between the $3s^{-1}4p$ and several light-induced states indicates the formation of polariton multiplets. We measure a controllable stabilization of the polaritons against ionization, in excellent agreement with \emph{ab initio} theory. Using an extension of the Jaynes-Cummings model to autoionizing states, we show that this stabilization is due to the destructive interference between the Auger decay and the radiative ionization of the polaritonic components. These results give new insights into the optical control of electronic structure in the continuum, and unlock the door to applications of autoionizing polaritons in poly-electronic systems.