Tracking Charge Migration with Frequency-Matched Strobo-Spectroscopy

TL;DR

This paper introduces frequency-matched strobo-spectroscopy (FMSS) combined with high-harmonic generation to track charge migration dynamics in molecules with attosecond resolution, revealing phase-sensitive electron density changes.

Contribution

The study demonstrates a novel pump-probe scheme using HHG-driven lasers to monitor charge migration with high temporal resolution, highlighting the role of recombination in HHG signal modulation.

Findings

Harmonic yield tracks charge migration phase.

Recombination dominates HHG modulation.

Attosecond resolution of charge dynamics achieved.

Abstract

We present frequency-matched strobo-spectroscopy (FMSS) of charge migration (CM) in bromobutadiyne, simulated with time-dependent density-functional theory. CM+FMSS is a pump-probe scheme that uses a frequency-matched HHG-driving laser as an independent probe step following the creation of a localized hole on the bromine atom that induces CM dynamics. We show that the delay-dependent harmonic yield tracks the phase of the CM dynamics through its sensitivity to the amount of electron density on the bromine end of the molecule. FMSS takes advantage of the intrinsic attosecond time resolution of the HHG process, in which different harmonics are emitted at different times and thus probe different locations of the electron hole. Finally, we show that the CM-induced modulation of the HHG signal is dominated by the recombination step of the HHG process, with negligible contribution from the ionization step.