arXiv subjects

Victor Despré

Publications and source records attributed to Victor Despré.

9 recordsLinked to original sources

arXiv2026

Real-time simulation of charge migration within the time-dependent Kohn-Sham DFT

Attosecond technologies provide unique opportunities to study electron dynamics and electron correlation on their intrinsic timescales. From a theoretical perspective, this places strong constraints as an accurate treatment of electron correlation is required. Recently, it was demonstrated that time-dependent density-functional theory (TDDFT) is capable of correctly predicting correlation-driven charge migration arising from hole mixing following ionization of the highest occupied molecular orbital (HOMO). Given the ability of TDDFT to treat large-scale systems, this approach offers promising perspectives for investigating electron-correlation-driven mechanisms in complex molecules. In this work, we assessed the constraints and limitations associated with using TDDFT to study this mechanism. We found that the charge-migration dynamics are already correctly reproduced using local-density approximation for the exchange-correlation functional, provided the states involved in the coherent superposition are well described within the TDDFT. However, for dynamics triggered by the ionization of orbitals below the HOMO, artificial ultrafast dynamics may appear on top of the charge-migration dynamics. These artifacts indicate that careful analysis of the simulated dynamics is required in order to reliably predict phenomena that could be observed experimentally.

physics.chem-ph↗

arXiv2026

Role of Metastable Dicationic Intermediates in the Breakup of CH$_4^{2+}$

We investigate the fragmentation dynamics of methane dication (CH$_4^{2+}$) produced in collisions with 50-MeV C$^{6+}$ ions using the COLTRIMS technique. The method provides complete three-dimensional momentum vectors of the charged fragments, enabling full kinematic reconstruction of the fragmentation process. The dynamics are analyzed using Dalitz plots, Newton diagrams, and the native-frame method to distinguish between concerted and sequential dissociation mechanisms. The data indicate the presence of sequential fragmentation pathways for the CH$_4^{2+}$ $\rightarrow$ CH$_2^+$ + H$^+$ + H, CH$_4^{2+}$ $\rightarrow$ CH$^+$ + H$^+$ + 2H, and CH$_4^{2+}$ $\rightarrow$ C$^+$ + H$^+$ + 3H channels, consistent with dissociation via short-lived dicationic intermediates CH$_3^{2+}$, CH$_2^{2+}$, and CH$^{2+}$, respectively. From the Newton-diagram momentum distributions, we further estimate the half-rotational periods of the intermediate states, providing insight into their rotational dynamics and finite lifetimes prior to fragmentation. The experimental observations are further supported by comparisons with calculated potential-energy curves.

physics.atom-ph↗

arXiv2026

Tailoring Attosecond Charge Migration in Native Molecular Ions

Attosecond chemistry involves developing strategies to manipulate electronic coherent waves in molecules, which can influence the outcome of photoinduced reactions. While recent progress in this field calls for investigations of increasingly complex isolated or embedded systems, theoretical predictions on attosecond charge migration have remained limited to native neutral species. Since molecules in nature often carry a native charge, there is potential biological and chemical interest in determining whether attosecond charge migration is affected by an additional charge. In this study, we employ high-level correlated methods to study purely electronic dynamics induced by hole-mixing in molecular ions. Our results, obtained for a series of neutral, protonated and deprotonated molecules, reveal that the likelihood of observing attosecond electron dynamics can either be degraded or improved by the presence of an initial charge, and that the existence of the dynamics is correlated with the strength of electron correlation. These findings will stimulate further experimental and theoretical investigations into this unexplored field of attosecond dynamics in molecular ions.

physics.chem-ph↗

arXiv2026

Surface Plasmons in the Continuum

The interest to foster plasmonic applications at energies in the ultra-violet, has escalated research initiatives in clusters of unconventional plasmonic materials like aluminum and indium,for which the surface-plasmon resonance appears above the ionization potential. Naturally, the quantum mechanical description calls for the incorporation of the ionization process, thereby making the ab initio calculations challenging. We present a robust approach within the time-evolution formalism of the time-dependent density-functional theory to calculate surface plasmon resonance in the continuum of metal clusters. Using the much studied Al$_{13}^-$ as a system of reference, we show that accurate description of the continuum and of the ionization of the cluster allow to capture a broad surface-plasmon in the UV. Application of this approach in aluminum clusters has given the size-dependent evolution from discrete spectral features in Al$_{6}$ to the surface-plasmon in larger clusters in the deep ultra-violet.

physics.chem-ph↗

arXiv2024

Correlation-Driven Charge Migration Triggered by Infrared Multi-Photon Ionization

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 using 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 HOMO of a molecule.

physics.chem-ph↗

arXiv2023

Size effect in correlation-driven charge migration in correlation bands of alkyne chains

Correlation-driven charge migration initiated by inner-valence ionization leading to the population of the correlation bands of alkyne chains containing between 4 and 12 carbon atoms is explored through ab initio simulations. Scaling laws are observed, both for the timescale of the charge migration and for the slope of the density of states of the correlation bands. Those can be used for predicting the relaxation time scale in much larger systems from the same molecular family and for finding promising candidates for the development of attochemistry scheme taking advantages of the specificity of the dynamics in correlation bands of molecules.

physics.chem-ph↗

arXiv2023

Observation of Nuclear-wavepacket Interference in Ultrafast Inter-atomic Energy Transfer

We report the experimental observation of quantum interference in the nuclear wave-packet dynamics driving ultrafast excitation-energy transfer in argon dimers below the threshold of interatomic Coulombic decay (ICD). Using time-resolved photoion-photoion coincidence spectroscopy and quantum dynamics simulations, we reveal that the electronic relaxation dynamics of the inner-valence $3s$ hole on one atom leading to a $4s$ or $4p$ excitation on the other one is influenced by nuclear quantum dynamics in the initial state, giving rise to a deep, periodic modulation on the kinetic-energy-release (KER) spectra of the coincident Ar$^+$-Ar$^+$ ion pairs. Moreover, the time-resolved KER spectra show characteristic fingerprints of quantum interference effects during the energy-transfer process. Our findings pave the way to elucidating quantum-interference effects in ultrafast charge- and energy-transfer dynamics in more complex systems.

physics.atm-clus↗

arXiv2021

Correlation-Driven Charge Migration as Initial Step in the Dynamics in Correlation Bands

We present dynamics calculations showing how electron-correlation-driven charge migration occurring in the correlation band of ionized molecules can lead to a redistribution of the charge increasing the stability of the system. These calculations offer an interpretation of recent experimental results obtained for adenine. We discuss the implications of the mechanism for the development of attochemistry and how it can be understood in the context of the ultrafast, non-adiabatic relaxation taking place in highly-excited molecular cations.

physics.chem-ph↗

arXiv2021

Decoherence and Revival in Attosecond Charge Migration Driven by Non-adiabatic Dynamics

Attosecond charge migration is a periodic evolution of the charge density of a molecule on a time scale defined by the energy intervals between the electronic states involved. Here, we report the observation of charge migration in neutral silane (SiH$_4$) in 690~as, its decoherence within 15~fs, and its revival after 40-50~fs using X-ray attosecond transient absorption spectroscopy. The migration of charge is observed as pairs of quantum beats with a characteristic spectral phase in the transient spectrum. The decay and revival of the degree of electronic coherence is found to be a result of both adiabatic and non-adiabatic dynamics in the populated Rydberg and valence states. The experimental results are supported by fully quantum-mechanical {\it ab-initio} calculations that include both electronic and nuclear dynamics. We find that conical intersections can mediate the transfer of electronic coherence from an initial superposition state to another one involving a different lower-lying state. Operating on neutral molecules, our methods define a general approach to the key phenomena underlying attochemistry.

physics.chem-ph↗