Laser Stabilised Ionising Transitions

TL;DR

This paper explores how resonant laser pumping creates a new metastable ionising state in atoms, with unique fluorescence spectra, offering a novel method to stabilize and engineer non-classical electronic states using intense laser fields.

Contribution

It introduces a new metastable ionising state formed under resonant laser excitation, distinct from previous non-perturbative stabilization methods, and analyzes its fluorescence properties.

Findings

Creation of a metastable ionising state above a critical pump intensity

Distinct fluorescence spectrum from traditional bound-to-bound transitions

Potential for stabilizing electronic states with intense lasers

Abstract

We investigate a ionising electronic transition under resonant pumping. We demonstrate that, above a critical value of the pump intensity, a novel metastable electronic bound state is created, which can decay into the free electron continuum by two-photon ionization. We calculate the system's resonant fluorescence spectrum, finding results qualitatively different from the Mollow triplet expected in a bound-to-bound transition. The fluorescent emission can be used to measure the time-resolved population of the novel metastable state. Contrary to Kramers-Hennenberger atoms, stabilised by non-perturbative, non-resonant laser pulses, the physics we observe is inherently resonant and relies on perturbative level repulsion. In analogy to how the AC-Stark shift is a semiclassical version of the single-photon Rabi splitting observed in photonic cavity, the phenomenon we describe is better understood as a semiclassical version of recently observed excitons bound by a single cavity photon. Our results demonstrate a novel way to stabilise electronic states with intense laser fields, increasing our capability to design and engineer non-classical states of matter.