# Exact single-electron approach to the dynamics of molecules in strong laser fields

## TL;DR

This paper introduces an exact single-electron framework for modeling correlated electron dynamics in molecules under strong laser fields, providing a new perspective on single-electron approximations.

## Contribution

It develops an exact factorization-based single-electron approach and derives an approximation that advances ab-initio modeling of molecular electron dynamics.

## Key findings

- Exact and approximate potentials yield similar dynamics in low ionization scenarios.
- The ionization barrier can be explicitly time-dependent in the model.
- The approach challenges traditional interpretations of the single-active electron approximation.

## Abstract

We present an exact single-electron picture that describes the correlated electron dynamics in strong laser fields. Our approach is based on the factorization of the electronic wavefunction as a product of a marginal and a conditional amplitude. The marginal amplitude, which depends only on one electronic coordinate and yields the exact one-electron density and current density, obeys a time-dependent Schr\"odinger equation with an effective time-dependent potential. The exact equations are used to derive an approximation that is a step towards a general and feasible ab-initio single-electron approximation for molecules. The derivation also challenges the usual interpretation of the single-active electron approximation. From the study of model systems, we find that the exact and approximate single-electron potentials for processes with negligible two-electron ionization lead to a qualitatively similar dynamics, but that the ionization barrier may be explicitly time-dependent.