Laser-induced electron diffraction in the over-the-barrier ionization (OBI) regime

TL;DR

This paper investigates whether laser-induced electron diffraction (LIED) can still effectively image molecular structures in the over-the-barrier ionization (OBI) regime, using classical and quantum models to demonstrate its viability.

Contribution

It demonstrates through theoretical models that LIED can retrieve molecular structure information even in the OBI ionization regime, expanding its applicability.

Findings

LIED can be described by classical recollision models in the OBI regime

Structure retrieval from LIED is possible despite short trajectory contributions

The study supports real-time imaging of chemical transformations in large molecules

Abstract

Large polyatomic molecules typically exhibit low ionization potentials, Ip, leading to over-the-barrier ionization (OBI) already at relatively low intensities (~1013 W/cm2). We revisit laser-induced electron diffraction (LIED) in the over-the-barrier ionization (OBI) regime and answer the question of whether imaging of molecular structure is still possible with LIED. We employ a hydrogen-like model system mimicking a molecule with low Ip using a classical trajectory-based model (CT) that incorporates the Coulomb potential; we also use the numerical solution to the time-dependent Schrodinger equation (TDSE). Specifically, we adopt the Fourier transform variant of LIED (FT-LIED) to show that even a significant contribution of short trajectories in the OBI regime does not preclude structure retrieval from strong-field diffractive patterns. This theoretical investigation shows that LIED can be well described by the classical recollision model even when ionization occurs within the OBI regime. This study paves the way towards strong-field imaging of chemical transformations of large polyatomic molecules in real-time based on strong-field electron recollision.