arXiv subjects

Nicolas Sisourat

Publications and source records attributed to Nicolas Sisourat.

6 recordsLinked to original sources

arXiv2026

Semiclassical description of Intermolecular Coulombic Electron Capture in solutions

In this work, we present a semiclassical approach to model Intermolecular Coulombic Electron Capture (ICEC) in aqueous solutions using molecular dynamics simulations with OpenMM. We investigate the behavior of an excess electron in the presence of cations (Fe$^{3+}$) in water, focusing on the influence of electron energy and cation concentration on the ICEC quantum yield. Our simulations reveal that the ICEC quantum yield approaches unity at higher concentrations and initial electron energies, while it decreases at lower concentrations due to electron energy loss before reaching the cation.

physics.atom-ph↗

arXiv2025

Influence of vibrational motion and temperature on interatomic Coulombic electron capture

Interatomic Coulombic Electron Capture (ICEC) is an environment-mediated process in which a free electron attaches to a species by transferring excess energy to a neighbor. While previous theoretical investigations assumed fixed nuclei, recent studies indicate that nuclear dynamics significantly influences the ICEC process. In this work, we incorporate the vibrational motion into an analytical model of the ICEC cross section including both energy and electron transfer. To validate this approach, we compare the results to the adiabatic-nuclei approximation based on fixed-nuclei ab initio R-matrix calculations. We apply our theory to the helium-neon dimer, which is ideal for studying diverse dynamical effects. We show that while vibrational dynamics can slightly reduce ICEC efficiency, ICEC remains dominant over photorecombination and can trigger dimer dissociation. Accounting for the nuclear motion also enables to describe the broadening of the electron spectrum and enables evaluation of temperature-dependent cross sections - capabilities beyond the reach of fixed-nuclei approaches.

quant-ph↗

arXiv2023

Water-assisted electron capture exceeds photorecombination in biological conditions

A decade ago, an electron-attachment process called interatomic Coulombic electron capture has been predicted to be possible through energy transfer to a nearby neighbor. It has been estimated to be competitive with environment-independent photorecombination, but its general relevance has yet to be established. Here, we evaluate the capability of alkali and alkaline earth metal cations to capture a free electron by assistance from a nearby water molecule. We introduce a characteristic distance $r_{IC}$ for this energy transfer mechanism in equivalence to the Förster radius. Our results show that water-assisted electron capture dominates over photorecombination beyond the second hydration shell of each cation for electron energies above a threshold. The assisted capture reaches distances equivalent to a fifth to seventh solvation shell for the studied cations. The far reach of the assisted electron capture is of significant general interest to the broad spectrum of research fields dealing with low-energy electrons, in particular radiation-induced damage of biomolecules. The here introduced distance measure will enable quantification of the role of the environment for assisted electron attachment.

physics.chem-ph↗

arXiv2022

Theoretical study of the I$^{+}$ + I$^{-}$ mutual neutralization reaction

We have computed the cross sections of the mutual neutralization reaction between I$^{+}$ and I$^{-}$ for a collision energy varying from 0.001 eV to 50 eV. These cross sections were obtained using the adiabatic potential energy curves of the I$_{2}$ system computed with a direct relativistic Multi-Reference Configuration Interaction method and a semi-classical approach (i.e. Landau Zener Surface Hopping). We report the cross sections towards the following neutral states: $\text{I}(^{2}P_{3/2})+\text{I}(^{2}P_{3/2})$, $\text{I}(^{2}P_{3/2})+\text{I}(^{2}P_{1/2})$, $\text{I}(^{2}P_{1/2})+\text{I}(^{2}P_{1/2})$ and $\text{I}(5p^{4}6s)+\text{I}(^{2}P_{3/2})$. We also discuss the cross sections towards the two following excited ionic states : $\text{I}^{-}(^{1}S_{0})+\text{I}^{+}(^{3}P_{0})$ and $\text{I}^{-}(^{1}S_{0})+\text{I}^{+}(^{3}D_{2})$. The results of these calculations are in accordance with recent experimental measurements conducted in the double ion ring DESIREE in Stockholm. These results can be used to model iodine plasma kinetics and thus to improve our understanding of the latter.

physics.atom-ph↗

arXiv2022

Time-resolved Ultrafast Interatomic Coulombic Decay in Superexcited Sodium-doped Helium Nanodroplets

The autoionization dynamics of superexcited superfluid He nanodroplets doped with Na atoms is studied by extreme-ultraviolet (XUV) time-resolved electron spectroscopy. Following excitation into the higher-lying droplet absorption band, the droplet relaxes into the lowest metastable atomic $1s2s$ $^{1,\,3}$S states from which Interatomic Coulombic Decay (ICD) takes places either between two excited He atoms or between an excited He atom and a Na atom attached to the droplet surface. Four main ICD channels are identified and their time constants are determined by varying the delay between the XUV pulse and a UV pulse that ionizes the initial excited state and thereby quenches ICD. The time constants for the different channels all fall in the range $\sim$1~ps indicating that the ICD dynamics are mainly determined by the droplet environment. A periodic modulation of the transient ICD signals is tentatively attributed to the oscillation of the bubble forming around the localized He excitation. The ICD efficiency depends on the total number of excited states in a droplet rather than the density of excited states pointing to a collective enhancement of ICD.

physics.atm-clus↗

arXiv2018

The virtual photon approximation for three-body interatomic Coulombic decay

Interatomic Coulombic decay (ICD) is a mechanism which allows microscopic objects to rapidly exchange energy. When the two objects are distant, the energy transfer between the donor and acceptor species takes place via the exchange of a virtual photon. On the contrary, recent ab initio calculations have revealed that the presence of a third passive species can significantly enhance the ICD rate at short distances due to the effects of electronic wave function overlap and charge transfer states [Phys. Rev. Lett. 119, 083403 (2017)]. Here, we develop a virtual photon description of three-body ICD, showing that a mediator atom can have a significant influence at much larger distances. In this regime, this impact is due to the scattering of virtual photons off the mediator, allowing for simple analytical results and being manifest in a distinct geometry-dependence which includes interference effects. As a striking example, we show that in the retarded regime ICD can be substantially enhanced or suppressed depending on the position of the ICD-inactive object, even if the latter is far from both donor and acceptor species.

quant-ph↗