Correlation-driven charge migration triggered by infrared multi-photon ionization

Abstract

The possibility of observing correlation-driven charge migration has been a driving force behind theoretical and experimental developments in the field of attosecond molecular science since its inception. Despite significant accomplishments, the unambiguous experimental observation of this quantum beating remains elusive. In this work, we present a method to selectively trigger such dynamics in molecules predicted to exhibit long-lived electron coherence. We show that these dynamics can be selectively triggered using infrared multi-photon ionization and probed using the spacial resolution of X-ray free-electron laser, proposing a promising experimental scheme to study these pivotal dynamics. Additionally, we demonstrate that real-time time-dependent density-functional theory can describe correlation-driven charge migration resulting from a hole mixing structure involving the highest occupied molecular orbital of a molecule.

Fig. 1. The time-dependent oscillation of the hole density projected along the molecular axis due to the sudden ionization of the HOMO of propiolic acid (a), but-3-ynal (b), 3-pyrroline (c), and 2,5-dihydrofuran (d) is shown through color maps. The left-most column shows the molecules with their molecular axes oriented along the x-axis (cf., axes arrows). The third column represents calculations using TDDFT and compares to the results obtained in ADC as shown in the second one. The values of the hole density are represented by the color bar (a negative hole density means an excess of electron). For the TDDFT results, the localization of the hole-density corresponding to a crests (C) and a trough (T) of the oscillatory dynamics is presented as iso-surface in the last two columns. The iso-values are 0.005 e Å⁻³ for (a) and (b), and 0.008 e Å⁻³ for (c) and (d).

Fig. 2. Time-dependent hole density (left panels) and its Fourier transform (right panels) for propiolic acid projected along the molecular axis, shown as the y-axis of each panel, following multi-photon ionization triggered by an (a) even or (b) odd laser pulse, as illustrated above each panel. The hole density is normalized to its maximum value.

Fig. 3. Time-dependent hole density (left panels) and its Fourier transform (right panels) for propiolic acid projected along the molecular axis, shown as the y-axis of each panel, following multi-photon ionization triggered by the even pulse shown above the panels averaged over (a) 17 and (b) 8 orientation (see text). The hole density is normalized to its maximum value.