Optical absorption in atoms and molecules near laser-induced exceptional points

TL;DR

This paper develops a non-Hermitian theoretical framework to analyze optical absorption in atoms and molecules near laser-induced exceptional points, revealing how laser parameters can dramatically alter absorption spectra, with applications demonstrated on helium and xenon.

Contribution

It introduces a novel non-Hermitian approach to atomic and molecular absorption and a method to induce and analyze exceptional points using laser parameters.

Findings

Laser parameters can cause dramatic changes in absorption lineshapes.

The theory accurately predicts absorption spectra without fitting parameters.

Derived a simple formula for the Fano asymmetry factor.

Abstract

We present a non-Hermitian theory of atomic and molecular absorption, which enables computing the absorption spectrum of multi-electron atoms and molecules without using any fitting parameters. We propose a method for optically inducing exceptional points in atomic systems, and show that slight changes in the laser parameters may lead to dramatic changes in the absorption lineshape. We demonstrate these predictions for helium using exact ab-initio electronic-structure data. Finally, we derive a simple formula for the Fano asymmetry factor and evaluate it for a model xenon atom.