Strong-field ionization with few-cycle, mid-infrared laser pulses induces a localized ionization followed by long-lasting charge migration in halogenated organic molecules

TL;DR

This study demonstrates that few-cycle mid-infrared laser pulses can induce localized ionization and sustained charge migration in halogenated organic molecules, with potential control over molecular charge dynamics.

Contribution

It provides a detailed theoretical analysis showing how specific laser parameters can reliably initiate and sustain charge migration in organic molecules.

Findings

Charge migration is initiated by strong-field tunnel ionization at halogen sites.

The charge migration is robust across various laser wavelengths around 1500 nm.

Nuclear dynamics do not significantly disrupt the charge migration process.

Abstract

We show that applying a few-femtosecond mid-infrared laser pulse parallel to the backbone of a halogenated, conjugated organic molecule induces localized ionization followed by long-lasting field-free charge migration (CM). Through time-dependent density-functional theory calculations, we find that this CM is robust with respect to the parameters of the applied laser pulse. We document the spatial and temporal origin of the localized hole, which is initiated via strong-field tunnel ionization in the halogen end of the molecule, and near the peak of the laser electric field. In bromobutadiyne we find a range of wavelengths around $1500~\text{nm}$ that consistently leads to the initiation of high-contrast CM. In addition, we show that the inclusion of Ehrenfest nuclear dynamics does not disrupt the creation of the localized hole, nor the subsequent CM motion, in bromobutadiyne or \emph{para}-bromoaniline.