SEMINAIRES



 

Exploring the limits of Machine Learning Algorithms for the classification of X-ray absorption spectra

Mardi 19 mars 2024 à 11h
Salle 101 de l’UFR de Chimie, couloir 32-42  

Marius Retegan

The European Synchrotron Facility, Grenoble

marius.retegan@esrf.fr

 

      X-ray absorption spectroscopy gives access to a wealth of information regarding the local structure and electronic properties of materials. However, data analysis is significantly more time-consuming than the acquisition and initial data reduction. Decoding the information relies on comparison with similar compounds for which the spectrum-property mapping is already established, a task that is very often performed by visual inspection.

    Machine learning (ML) is revolutionizing many fields with its ability to extract and learn patterns in big data without having to provide additional prior information other than the data itself. ML models give access to instantaneous predictions of properties and observables, which makes them particularly attractive for performing real-time analysis of the measured data or autonomous experimental acquisitions.

     In this talk, I will present the application of the random forests algorithm and convolutional neural networks to identify the coordination environment of iron in a given compound from the corresponding K-edge X-ray absorption spectrum. As we train the models using theoretical data, but we use them to infer properties on measured spectra, I will analyze the different sources of errors that limit the quality of the prediction, such as spectral shift, normalization, and Poisson noise level. In addition, I will explore the use of oversampling techniques to tackle class imbalance, a common issue in such datasets, as most materials in nature tend to adopt a small set of specific coordination environments.


 

Pourquoi les dimères de van der Waals attirent-ils autant d’attention?

 

11 Mars 2024 à 11h, Salle 107 au Centre International de Conférences Sorbonne Université.

 

Dr Amine CASSIMI

Laboratoire CIMAP, CEA/CNRS/ENSICAEN/UNICAEN

Caen 

Depuis plus d’une décennie, de nombreuses études tant théoriques qu’expérimentales ont été dédiées aux dimères van der Waals, qu’ils soient atomiques ou moléculaires, attestant ainsi de leur intérêt croissant dans la communauté scientifique. Leur caractéristique la plus surprenante est l’aptitude des monomères à interagir à grande distance par l’intermédiaire de divers processus électroniques récemment mis en évidence tel que « l’Interatomic Coulombic Decay (ICD) » [1, 2]. Mais l’intérêt pour ces systèmes peu liés vient également de la quantité de nouvelles informations sur les monomères à laquelle ils donnent accès, notamment dans le cas des collisions avec des ions. En effet, l’un des premiers résultats a été de montrer expérimentalement qu’un dimère se comporte comme l’association de deux monomères quasi-indépendants. Cet exposé présentera une brève revue des résultats obtenus à l’aide des faisceaux d’ions du GANIL, Caen. 

[1] : L.S.Cederbaum et al, Phys. Rev. Lett. 79, 4778 (1997)

[2] : T. Jahnke et al., J. Phys. B 40, 2597 (2007)


 

Imaging ultrafast and ultrasmall: Unraveling nanoscale electronic and magnetic behavior using time-resolved x-ray scattering

Jeudi 7 mars 2024 à 10h30
Salle 101 de l’UFR de Chimie, couloir 32-42  

Roopali KUKREJA

Assistant Professor at UC Davis (USA)

 

Ultrafast laser control of correlated materials has emerged as a fascinating avenue of manipulating magnetic and electronic behavior at femtosecond timescales. Ultrafast manipulation of these materials has also been envisioned as a new paradigm for next generation memory and data storage devices. Numerous studies have been performed to understand the mechanism underlying laser excitation. However, it has been recently recognized that spatial domain structure and nanoscale heterogeneities can play a critical role in dictating ultrafast behavior.  In this talk, I will discuss methods and our recent results which capture material behavior at nanoscale lengthscales and femtosecond-nanosecond timescales. I will describe our recent experimental studies using emerging synchrotron techniques and free electron lasersuch as European XFEL and FERMI. In the first part of my talk, I will discuss our results on ultrafast magnetization dynamics where we uncovered a symmetry-dependent behavior of the ultrafast response. Labyrinth domain structure with no translation symmetry exhibit an ultrafast shift in their isotropic diffraction peak position that indicates their spatial rearrangement. On the other hand, anisotropic domains with translation symmetry do not exhibit any modification of their anisotropic diffraction peak position. In the second part of my talk, I will focus on x-ray imaging of correlated oxides and discuss spatially dependent ultrafast response observed in complex oxides such as rare-earth nickelates. These intriguing observation suggests preferential, texture-dependent paths not only for the transport of angular momentum, but also for structural rearrangements. These measurements provide us with a unique way to study and manipulate spin, charge and lattice degrees of freedom.


Lithium in cementitious materials:
use, abuse and analytical challenges

 

Jeudi 7 mars 2024 à 14h
Salle 101 de l’UFR de Chimie, couloir 32-42

Dr. Vincent THIERY

MT Nord Europe, Institut Mines-Télécom
Centre for Materials and Processes, F-59000 Lille, France

 

While the importance of Li in batteries is now widely known not only for scientists and for the general public, there are, of course, some lesser known applications. This is typically the case for cementitious materials. Indeed, various lithium salts (lithium nitrate, lithium carbonate, ...) are known to have effects on the hydration and long-term behaviour of concrete. Considering the difficulty to analyze both cementitious materials, which are a complex microstructural mixture of calcium silicate hydrates and other various hydrous phases, and lithium, this use offers interesting research
perspectives. We will review and discuss some examples.

 


Core excitation and decay dynamics of ions in water

Vendredi 26 Janvier 2024 à 14h30, Salle 101 de l’UFR de Chimie, couloir 32-42 

Olle Björneholm

Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden 

X-ray-induced core excitation and decay dynamics of isolated atoms is nowadays relatively well understood.How are such processes affected by an aqueous environment? In this presentation, I will discuss some recent studies on how solvating water molecules may participate in non-local processes, such as Intermolecular Coulombic Decay (ICD), Radiative Charge Transfer (RCT), and Electron Transfer Mediated Decay (ETMD) [1], in various stages of the core-hole excitation and decay. This includes results for ultrafast electron dynamics before the core-hole decay, both ICD [2] and RCT processes in the core-hole decay, as well as ETMD processes taking place in the highly charged ion formed by Auger decay [3], for neon-like Na+, Mg2+, and Al3+ions in water.

 

[1] Interatomic and Intermolecular Coulombic Decay, T. Jahnke et al., Chem. Rev. 120, 20, 11295 (2020) https://doi.org/10.1021/acs.chemrev.0c00106

[2] Probing Aqueous Ions with Non-local Auger Relaxation, G. Gopakumar et al., Physical Chemistry Chemical Physics 24, 8661 (2022) https://doi.org/10.1039/D2CP00227B 

[3] Radiation damage by extensive local water ionization from two-step electron transfer-mediated decay of solvated ions, G. Gopakumar et al., Nature Chemistry 15, 1408 (2023) https://doi.org/10.1038/s41557-023-01302-1

 


Ground-state, core and valence properties of heavy element species from relativistic
coupled cluster calculations

Lundi 15 Janvier 2024 à 14h00, Salle 101 de l’UFR de Chimie, couloir 32-42 


André Severo Pereira Gomes
1. Univ. Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, F-59000 Lille, France

andre.gomes@univ-lille.fr

Abstract: Accurate electronic structure calculations have become an indispensable tool to understand the molecular properties of heavy and superheavy elements. Such approaches help make sense of the underlying complex physical processes probed by experiments, or in the case such experiments are unfeasible due to the heavy elements’ radiotoxicity. In this presentation I will outline our contributions to developments of coupled cluster approaches based on four-component Hamiltonians for ground-state properties as well as for valence and core excitation and ionization spectra and their application to investigating actinides and super heavy elements [1-7]. Furthermore, I will outline how these can be combined with more approximate approaches through embedding theories [8, 9], to enable the investigation of species in complex environments such as in solution.


[1] J Pototschnig et al., JCTC (2021) 17, 5509 10.1021/acs.jctc.1c00260
[2] A Shee, T Saue, L Visscher, ASP Gomes, JCP (2018) 149, 174113 10.1063/1.5053846
[3] L. Halbert et al., JCTC (2021) 17, 3583 10.1021/acs.jctc.0c01203
[4] L. Halbert, ASP Gomes, Mol. Phys. (2023) e2246592 10.1080/00268976.2023.2246592
[5] X Yuan et al., arXiv:2307.14296, 2023
[6] X Yuan et al., arXiv:2309.07295, 2023
[7] S Kervazo et al., IC (2019) 58, 14507 10.1021/acs.inorgchem.9b02096
[8] Y. Bouchafra et al., PRL (2018) 121, 266001 10.1103/PhysRevLett.121.266001
[9] RA Opoku et al, PCCP (2022) 24, 14390 10.1039/d1cp05836c


Following complex spin structures in time & space

Mercredi 25 Octobre 2023 à 11h00, Salle 101 de l’UFR de Chimie, couloir 32-42  

Daniel Schick

 Junior Group Leader @ Max Born Institute, Berlin, Germany

Abstract: Controlling ultrafast spin dynamics directly on a quantum level by femtosecond light pulses promises a dramatic increase in speed, energy efficiency, and density of how we transport, process, and store information. Recent advances in the field have enabled an understanding of laser-driven spin dynamics from microscopic processes toward macroscopic functionality in magnetic nanostructures, including charge and spin transport as well as interactions with spatially extended quasiparticles such as phonons and magnons. These processes generally lead to a nanoscale spatial rearrangement of magnetization, calling for experimental techniques that can directly access the ultrafast evolution of spatially inhomogeneous spin profiles and detect the transfer or accumulation of spins at interfaces. Such observables providing nanometer spatial and femto- to picosecond temporal resolution are particularly required for investigations of complex heterostructures and antiferromagnets, where competing interactions result in a variety of complex spin structures already in equilibrium.

In this talk, I will focus on time-resolved resonant soft-X-ray scattering (RSXS) as a unique technique for probing magnetic order in time and space with element-selectivity as well as in buried layers. RSXS combines large spectroscopic and magnetic contrast in the soft-X-ray range with access to reciprocal space in addition to nanometer depth- and lateral spatial resolution. Based on the in-house development of two laser-driven soft-X-ray sources at Max Born Institute, we have recently demonstrated the feasibility of time-resolved RSXS in laboratory experiments as a true alternative to large-scale facilities. I will discuss our recent RSXS results on the dynamics of artificial antiferromagnets, ferromagnetic domains and magnons, as well as all-optical switching in ferrimagnetic alloys.


Sub-picosecond magnetization reversal of ferromagnets with spin currents

 

Mercredi 18 Octobre 2023 à 14h00, Salle 101 de l’UFR de Chimie, couloir 32-42  

Quentin Remy

Department of Physics, Freie Universität Berlin

 

Abstract:Since the discovery of ultrafast demagnetization of ferromagnets in 1996 [1], the ultrafast magnetism community had to face many theoretical and experimental challenges to trigger and observe various types of ultrafast (sub-picosecond) spin dynamics as well as to understand their underlying mechanisms. While many questions are still open [2], the specific topic of magnetization reversal (also called switching) is of great fundamental interest, to understand for example magnetization dynamics in the nonlinear regime and the dynamics of phase transitions, on top of its potential applications for data storage devices.

In this seminar, I will present how one can reverse the magnetization of ferromagnets using external spin currents coming from the laser-pulse induced demagnetization of a ferrimagnetic GdFeCo layer [3]. The bipolar temporal shape of the spin current is seen to control the dynamics of the magnetization of the ferromagnet when the latter is nearly quenched [4] leading to a magnetization switching within a few hundred of femtoseconds. Finally, I will show that one can design a simple fully ferromagnetic heterostructure (free of rare-earth materials) where the direction of the magnetization is dictated by the laser pulse energy [5]. These results are supported by a model which supports a complex interplay between magnetization dynamics and spin transport [6].  

[1] E. Beaurepaire, J.-C. Merle, A. Daunois, and J.-Y. Bigot, Phys. Rev. Lett. 76, 4250 (1996).

[2] P. Scheid, Q. Remy, S. Lebègue, G. Malinowski, and S. Mangin, J. Magn. Magn. Mater. 560, 169596 (2022).

[3] S. Iihama et al., Adv. Mater. 30, 1804004 (2018); Q. Remy et al., Adv. Sci. 7, 2001996 (2020); J. Igarashi et al., Nano Lett. 20, 8654 (2020).

[4] Q. Remy et al., Nat. Commun. 14, 445 (2023).

[5] J. Igarashi et al., Nat. Mater. (2023).

[6] Q. Remy, Phys. Rev. B 107 174431 (2023).

 


Pourquoi les dimères de van der Waals attirent-ils autant d’attention?

Lundi 9 Octobre 2023 à 14h30, Salle 101 de l’UFR de Chimie, couloir 32-42 

Amine CASSIMI

Laboratoire CIMAP, CEA/CNRS/ENSICAEN/UNICAEN, Caen 

Abstract: Depuis plus d’une décennie, de nombreuses études tant théoriques qu’expérimentales ont été dédiées aux dimères van der Waals, qu’ils soient atomiques ou moléculaires, attestant ainsi de leur intérêt croissant dans la communauté scientifique. Leur caractéristique la plus surprenante est l’aptitude des monomères à interagir à grande distance par l’intermédiaire de divers processus électroniques récemment mis en évidence tel que « l’Interatomic Coulombic Decay (ICD) » [1, 2]. Mais l’intérêt pour ces systèmes peu liés vient également de la quantité de nouvelles informations sur les monomères à laquelle ils donnent accès, notamment dans le cas des collisions avec des ions. En effet, l’un des premiers résultats a été de montrer expérimentalement qu’un dimère se comporte comme l’association de deux monomères quasi-indépendants. Cet exposé présentera une brève revue des résultats obtenus à l’aide des faisceaux d’ions du GANIL, Caen. 

[1] : L.S.Cederbaum et al, Phys. Rev. Lett. 79, 4778 (1997)

[2] : T. Jahnke et al., J. Phys. B 40, 2597 (2007)


X-ray movies of ultrafast melting and boiling in plasmonic nanoparticles

 

Jeudi 6 Juillet 2023 à 15h, Salle 101 de l’UFR de Chimie, couloir 32-42 

 

Daniela Rupp

Nanostructures and Ultrafast X-ray Science, ETH Zürich

Abstract: Via single-shot coherent diffractive imaging (CDI), the structure and dynamics of isolated nanosamples can be directly visualized: Intense and short pulses of X-ray free-electron lasers (XFELs) or intense high-harmonic generation (HHG) based sources scatter off a free-flying nanostructure, forming an interference pattern that is captured with a large-area detector. With computer-based iterative phase-retrieval or forward-fitting methods a snapshot of the object’s structure can be retrieved from the pattern. This has opened a door for us to study intense laser-matter interaction with unprecedented detail.

In this seminar, I will give an introduction to the single-shot single-particle CDI method and discuss its capabilities on the example of the dynamics in laser-heated plasmonic nanoparticles. In recent experiments we brought silver nanoparticles into the gas phase and heated them with laser pulses tuned to their surface plasmon resonance. This approach allows for a uniform heating of the nanoparticles at comparably low laser intensities, avoiding strong-field effects like tunneling and electron impact ionization. We observe, depending on the heating laser’s intensity, a wide range of processes from surface melting to full melting, internal boiling, cavitation, expansion and inflation, droplet vibrations, up to explosive boiling. Molecular dynamics simulations show that the systems travel on rather similar trajectories through the phase diagram, differing only in whether and where the stability limit of the metastable superheated liquid is crossed.

These results exemplify the maturity of time-resolved single-particle coherent diffraction imaging for investigating ultrafast dynamics in matter, being now on a level where we can really extract previously inaccessible physical quantities of matter under extreme conditions.

 


FCInet: a classification neural network to describe the configuration interaction space

 

Lundi  5 Juin 2023 à 11h, Salle 101 de l’UFR de Chimie, couloir 32-42 

 

Bastien Casier

Université d’Artois, Lens, Hauts-de-France, France


Abstract:
In this study, we present an iterative machine learning classification algorithm to smartly select the most important Slater determinants used in the expansion of the electronic wave-function. The learnable information is encoded through a binary representation of the spin-orbital populations of each Slater determinant, while the learning is based on the minimization of the binary cross-entropy.
Today, this method presents very promising results for small molecules like CO, N2, H2O, NH3 and C2H6. The FCI accuracy have been obtained along the dissociation curve of diatomic systems by only selecting a small fraction of the Hilbert’s space. This primary study is a proof of principle of the binary classification of the Slater determinants for the selective CI methods.
Our end goal would be to realize a global learning on the full dissociation curves to define the first interaction potentials at the FCI level.

-- 

L’électron de Dirac, les constantes fondamentales, les déviations de leurs valeurs entières et la continuité entre les forces électrique et gravifique

jeudi  23 février 2023 à 15h Salle 101 de l’UFR de Chimie, couloir 32-42 

Jean Maruani  

En revisitant l'équation de Dirac, on conjecture que l'électron peut être vu comme une charge sans masse oscillant à la vitesse de la lumière : ce mouvement serait responsable de la masse au repos impliquée dans les mouvements et interactions externes (inertie et gravité), avec des implications sur les concepts d'espace, de temps, de masse, de charge électrique et de moment magnétique. Le facteur gyromagnétique ge2 introduit par cette équation peut s'expliquer par un battement électron-positron et par l'interaction de l'électron avec le champ du vide. Mais la constante de structure fine inverse de137 qui en découle aussi est l'objet de spéculations inabouties. Il en est de même de l'invariant gravitationnel dp construit sur une forme similaire. Les déviations de ge, ae et dp leurs valeurs entières approchées peuvent s’exprimer sous forme de séries limitées impliquant 137 et pi. Bien que les forces électrique et gravifique soient gouvernées par des théories très différentes, cette étude permet de proposer des schémas de conciliation originaux.


Electron spectroscopy of isolated atoms and molecules using hard X-ray synchrotron radiation

Vendredi 10 février 2023 à 15h Salle 101 de l’UFR de Chimie, couloir 32-42 

Ralph Püttner

Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin

Abstract: 

The usage of hard X-ray synchrotron radiation (hν = 2 – 14 keV) is a relatively new research field in atomic and molecular physics and has strongly developed in recent years due to improved light sources and electron analyzers. It allows to get access to deeper core holes like 1s-1 in the third and fourth row elements, and in combination with intense undulator beams even to double core holes like 1s-2 in elements as heavy as argon. After a short overview of research topics relevant in this energy regime I will focus on double core-hole (DCH) processes. First, the oxygen K-2V (V = valence) DCH spectrum of CO will be discussed and compared with the oxygen K-1V absorption spectrum of the same molecule, which reveals the influence of the second core hole of the otherwise similar states. After this, the Auger hypersatellites, i.e., the first-step Auger decays of K-2 states of neon, water, and argon will be presented. For neon, the achieved high experimental resolution allows to distinguish different DCH initial states like K-2 and K-2V based on different lineshapes. In the hypersatellite spectrum of water evidence of ultrafast dissociation dynamics on the 1 fs timescale is observed. Interestingly, the hypersatellite Auger spectrum of argon overlaps with a previously unobserved decay channel of the Ar 1s-13p-1nl photoelectron satellites, which is identified as a knock-down process.

 


Interaction de H et de O atomique avec un hydrocarbure aromatique polycyclique neutre ou ionisé

Lundi 28 Novembre 2022 à 14h30 Salle 101 de l’UFR de Chimie, couloir 32-42 

Morisset SabineRougeau Nathalie

Institut des Sciences Moléculaires d’Orsay ISMO UMR 8244 Université Paris-Saclay ; Orsay 

 Abstract:

Dans le milieu interstellaire (MIS), les grains de poussières servent de catalyseur à la réaction de formation de molécules telle que H2, OH … Selon les conditions, ces grains peuvent être carbonés, silicatés nus ou recouvert de glaces... Les hydrocarbures aromatiques polycycliques (HAP) sont connus pour être des réservoirs à carbone dans le MIS. Nous avons donc choisi d’étudier les interactions entre un atome H ou O avec un petit HAP modèle : le coronène (C24H12) neutre ou ionisé. Ces études ont pour but de comprendre les mécanismes d’addition, d’isomérisation et de fragmentations des HAP.  Lors de l’étude de l’interaction de O (3P) avec le coronene (1) , nous avons montré qu’il existe une voie qui implique des barrières faibles et qui mène de l’addition de O à la fragmentation du coronène et à la formation de la molécule de kétène, HCCO. Dans cet exposé je présenterai des résultats expérimentaux et théoriques sur ce système. Dans une deuxième partie, je parlerai des réactions d’hydrogénation successives du cation de coronène. Je présenterai les probabilités d’additions d’hydrogène et de formation de H2 obtenues par une méthode Monte Carlo Cinétique (KMC) en fonction des sites et des barrières à l’addition.

(1) F. Dulieu, S. Morisset, A. S Ibrahim Mohamed, L. Boschman, S. Cazaux, D. Billy, S.Baouche, N. Rougeau Molecular Astrophysics, 2019, 17, 100054


"Analyses physico-chimiques de matières colorantes dans les enluminures"

Jeudi 24 novembre 2022 a 11h, salle 101 de l'UFR de Chimie, couloir 32-42

Dr. Lucy Cooper

Bibliothèque nationale de France

Abstract:

La Bibliothèque nationale de France est un établissement sous tutelle du Ministère de la Culture. La BnF a pour mission de collecter, conserver, enrichir et promouvoir le patrimoine documentaire national. La BnF comprend son propre laboratoire scientifique qui, parmi ses tâches variées, effectue des analyses physico-chimiques sur les documents anciens et contemporains. Cette présentation se focalisera sur les études des manuscrits médiévaux illuminés par des techniques microscopiques et spectroscopiques, afin de déterminer la composition chimique des matières colorantes utilisées sur les enluminures. Les informations obtenues sur la palette employée sont utiles pour établir des préconisations de conservation mais également d'un point de vue technique de l'histoire de l'art.
Après une description des pigments et colorants utilisés au Moyen Age, je présenterai quelques exemples d'études menées à la BnF.


 

Detection and quantification of lithium for battery applications by using combinations of surface analysis techniques

Vendredi 9 Septembre 2022 à 9h45 Salle 101 de l’UFR de Chimie, couloir 32-42

De VITO Eric

Laboratoire de Caractérisation Avancée pour l’Energie, LITEN, Laboratoire d'innovation pour les technologies des énergies nouvelles et les nanomatériaux, CEA

Abstract:

The efficiency of Li-ion batteries (LIB) depends on multiple factors. Among them, the mobility of lithium in the solid electrolyte interphase (the so-called SEI), which forms at the surface of negative electrodes, as well as lithium mobility in the active material itself, is being thoroughly studied, though the complex underlying mechanisms are still misunderstood. In such context, the detection of lithium, the characterization of its chemical environment, its quantification, can be challenging. In this talk, studies based on surface analysis techniques, which allowed characterizing lithium in various systems related to LIB applications, will be reported. In addition, novel approaches based on lithium isotopic tracing, that are being developed at the lab, in order to study Li mobility in the SEI or in solid electrolytes (which may be used in future solid- state systems), will also be described.


 

From electrons to reactive flow: Multiscale modeling for heterogeneous
catalysis

Jeudi 7 Juillet 2022 à 14h00 Salle 101 de l’UFR de Chimie, couloir 32-42

MATERA Sebastian 
Theory Department, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
Institute for Mathematics, Freie Universität Berlin, Arnimallee 9, 14195 Berlin, Germany
 

Abstract:
Gaining an atomic scale insight into the driving forces behind heterogeneous catalysis under technologically relevant conditions is a major challenge. Besides experimental challenges, this is due to the intrinsic multiscale character of the problem. Bond making and bond breaking happens on electronic time and length scales, i.e. in the (sub-)femtosecond and (sub-)nanometer range. In the other extreme, a reaction chamber is a macroscopic device with a volume in the range of cubic centimeters and the continuous conversion of reactants to products by the catalysts might cause sizable concentration gradients within the chamber. In an in-situ experiment, such effects on different scales might interact in a nontrivial manner and modeling ideally addresses this coupling.
During the last years, we have developed such a multiscale modeling approach, which bridges between electronic structure and continuum level theories describing macroscopic mass and energy transport. In the first part of the talk, I will outline the ingredients of this methodology for the description of operando characterization of single crystal catalysts. Using this approach, possible complex phenomena in such experiments, e.g. chemistry driven non-chemical oscillations, will be discussed. Besides illustrative examples, I will address how this methodology in conjunction with experiment can help to shine light into the debated question of the active phase for the CO oxidation.
The second part of the talk will be devoted to the treatment of different, more complex scenarios, where the catalysts possess a mesoscopic structure. Particularly, I will present our work on the extension of the approach to powder catalysts and on the impact of inhomogeneous light absorption in photocatalytic particles.

 

 

Watching atoms and electrons in action with short wavelength free electron lasers

Mercredi 29 Juin 2022 à 10h30 Salle 101 de l’UFR de Chimie, couloir 32-42

Kiyoshi Ueda 
Tohoku University, Department of Chemistry, Sendai, JAPAN

Abstract:

The present seminar talk will illustrate the current status of short-wavelength free-electron laser (FEL) experiments, focusing on characteristic properties of different facilities.  The advent of hard x-ray FELs, such as SACLA in Japan, opened a route to extract a structure of a single nanoparticle [1] and its change upon the intense laser irradiation that transforms the nanoparticle into a nanoplasma [2]. The first high repetition rate soft x-ray FEL, European XFEL, combined with Reaction Microscope/COLTRIMS, made a long-standing dream to watch atoms in action, initiated by photoexcitation of a molecule, a tangible reality, using the so-called core-level photoelectron diffraction technique for fixed-in-space molecules [3]. Generations of two-color attosecond pulses at LCLS in the USA finally opened the door to watch charge migration in a molecule, before the nuclear dynamics sets in, with an attosecond transient absorption technique based on detections of resonant Auger electrons [4]. Generating phase-coherent multi-color pulses at FERMI, on the other hand, provided a novel approach to coherently control the electronic wave-packet [5] and to read out the photoionization phase [6]. These works were carried out by a wide range of international collaborations. I acknowledge all the collaborators in the authors list of [1-6] for fruitful collaborations. 

[1] A. Niozu et al. IUCrJ 7, 276 (2020); A. Niozu et al. PNAS 118, e2111747118 (2021).

[2] T. Nishiyama et al. PRL 123, 123201 (2019); A. Niozu et al. PRX 11, 031046 (2021).

[3] G. Kastire et al. PRX 10, 021052 (2020).

[4] T. Barillot et al. PRX 11, 031048 (2021).

[5] K. Prince et al. Nature Photonics 10, 176 (2016); D. Iablonskyi et al..PRL119, 073203 (2017).

[6] M. Di Fraia et al. PRL 123, 213904 (2019); D. You et al. PRX 10, 031070 (2020).


 
Tabletop facility for ultrafast soft x-ray absorption spectroscopy
 
Lundi 20 Juin 2022 à 10h30 Salle 101 de l’UFR de Chimie, couloir 32-42

Oscar Naranjo

University of Duisburg-Essen, Faculty of Physics, 47057 Duisburg,
e-mail: oscar.naranjo@uni-due.de
 
Abstract:

The recent development of tabletop soft x-ray sources based on high harmonic generation (HHG) has made systematic experiments on ultrafast soft x-ray absorption spectroscopy more accessible [1]. This development, however, remains challenging due to the required intense long-wavelength laser sources, especially in the mid-infrared spectral region. 

Here I present our latest results on HHG in a capillary using infrared pump pulses generated in a laser setup based on optical parametric chirped-pulse amplification (OPCPA) [2]. The OPCPA setup has been optimized by increasing the pump energy and by implementing a chirped mirror compressor. It generates sub-50 fs pulses at the central wavelengths of 1.5 and 3 µm with energies of 1.8 and 0.8 mJ, respectively, at the repetition rate of 100 Hz [3]. 

Harmonics up to 427th order (350 eV photon energy) produced with 1.5 µm pulses as a pump have been detected. A photon flux of 10^5 photons/s in a 1% bandwidth at 270 eV was reached. The measured beam divergence is about 2 mrad. The x-ray spectrometer used for the high harmonic detection has a resolution of about 2 eV. That allows us to perform X-ray absorption fine structure spectroscopy. The first spectra obtained of h-BN in transmission geometry are in good agreement with data available in the literature and will be presented. 

The authors acknowledge funding by the DFG through SFB 1242, TP A05.

 [1] J. Lloyd-Hughes et al., J. Phys.: Condens. Matter 33, 353001 (2021).

[2] M. Bridger, O. A. Naranjo-Montoya et al., Opt. Express 27, 31330 (2019). 

[3] O. A. Naranjo-Montoya et al., Compact EUV & X-ray Light Sources JW5A-10 (2022). 


 Tools and subjects of ultrafast physics: From highly efficient XUV generation through high-
order frequency mixing to chiral steering of free-induction decay

Mardi 14 Juin 2022 à 10h30 Salle 101 de l’UFR de Chimie, couloir 32-42

Margarita Khokhlova
Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Berlin
and Department of Physics, King’s College, London

 

Abstract:
In my talk I will present two examples from two current directions of development of ultrafast physics and attophysics.
The first direction is the advancement of attosecond sources: generation of more intense XUV pulses with a shorter duration. Here I will present a study of the generation of coherent XUV using intense laser fields in a rapidly ionising gas. We show that the blue shift during propagation is a dominant limitation for the high-harmonic generation efficiency for visible or near-UV drivers [1].
We introduce a new spatial scale, the blue-shift length, which sets the upper bound for the quadratic growth of the harmonics. Moreover, we show that this restriction can be overcome by adding a weak mid-IR field: the phase-matched high-order frequency-mixing process does not suffer from this blue shift, and the generated XUV intensity grows quadratically.
The second direction in which attoscience progresses is a discovery of new physical processes becoming accessible at these ultrafast timescales. In this part of my talk, I will give you an example of a new process we proposed – chiral steering of free-induction decay [2]. Chiral discrimination has recently become an emerging frontier in ultrafast physics, with vivid progress achieved in multiphoton and strong-field regimes.
Here we introduce a new phenomenon, enantiosensitive free-induction decay, steered by a tricolour chiral (TRICC) field structured in space and time. We demonstrate theoretically that an excited chiral molecule accumulates an enantiosensitive phase due to pertur-bative interactions with the TRICC field, resulting in a spatial phase gradient that steers the free-induction decay in opposite directions for opposite enantiomers.
[1] M A Khokhlova and V V Strelkov, ‘Highly efficient XUV generation via high-order frequency mixing’,New
J. Phys. 22 093030 (2020).
[2] M Khokhlova et al., ‘Enantiosensitive steering of free-induction decay’, Sci. Adv. 8, eabq1962 (2022)


Study of the Light-Induced ultrafast magnetization dynamics

Lundi 30 Mai 2022 à 14h Salle 101 de l’UFR de Chimie, couloir 32-42

Philippe Scheid

Université de Lorraine, IJL, CNRS, UMR 7198, BP 70239, 54000 Cedex Nancy, France

Abstract

The study of light–induced ultrafast magnetization dynamics was kick–started in 1996 by Beaurepaire et al. [1], who showed that a pulse of light of only 100 fs was capable of demagnetizing a thin film of Ni in less than 1 ps. The fact that traditional ways of manipulating the magnetization, utilizing a magnetic field or a current, require a far longer exposure made this discovery as much puzzling as it is promising regarding the development of future generations of data storage technologies. However, more than 25 years later, no consensus exists regarding both the nature of the excitations responsible for demagnetized state, and how they are triggered.
In this context, relying on ab initio calculations, and accounting for the effect of the light–pulse by a raised electronic temperature, we will discuss the suppression of the atomic magnetic moments [2], as well as the reduction of the inter–atomic exchange as possible sources of demagnetization.

Later on, in 2007, Stanciu et al. [3] discovered that a train of femtosecond pulses of light can trigger the so–called all–optical helicity–dependent switching (AO–HDS). Its presence has then been evidenced in many different types of magnetic thin films and provides a deterministic way to control the magnetization state, solely relying on the polarization of the light. While the origin of the AO–HDS is still debated, it is usually assumed to be induced by the inverse Faraday effect (IFE)[4], designating the generation of a magnetization proportional to the intensity of the circularly polarized light. Another effect, occurring simultaneously to the IFE in dissipative materials is the magnetization induced during light absorption [5] (MILA), which magnitude, contrary to the IFE, is proportional to the fluence of the light. Both effects will be discussed and compared, and their respective contribution will be examined, notably in the framework of real–time time–dependent density functional theory (RT–TDDFT) [6].

References

[1] E. Beaurepaire et al., Phys. Rev. Lett., 76, 4250 (1996).

[2] P. Scheid et al., Phys. Rev. B. 99 174415, (2019).

[3] C. D. Stanciu et al., Phys. Rev. Lett., 99 47601 (2007).

[4] L. P. Pitaevskii, J. Exptl. Theoret. Phys. (U.S.S.R.) 12 1450 (1961).

[5] P. Scheid et al., Phys. Rev. B. 100 214402 (2019).

[6] P. Scheid et al., Nano Letters 21 1943 (2021).

 
 

 

 
Interatomic Coulombic decay in ion-dimer collisions

Lundi 16 Mai 2022 à 11h Salle 101 de l’UFR de Chimie, couloir 32-42

Tom Kirchner
 
York University, CANADA

Abstract:
Free-electron production is an exceedingly rare process in low-energy ion-atom and ion-molecule collisions. This may change if the target monomer is replaced by a dimer (or a larger cluster) which allows for interatomic Coulombic decay (ICD), i.e., the transfer of enough excitation energy from one constituent to a neighbor so that an electron can be released from the latter.
ICD in neon dimers impacted by slow ions has recently been observed and semi-quantitatively explained by a classical over-the-barrier model calculation.
Using an independent-atom independent-electron model and a quantum mechanical description of the electron dynamics we were able to confirm the occurrence of ICD in 2.81 keV/amu triply-charged oxygen ion collisions after capture of an inner-valence Ne(2s) electron. We also showed that triply-charged lithium ions are far less efficient in initiating ICD because the energy level structure of these projectiles makes 2s capture unlikely.
Conversely, more recent calculations suggest that low-energy alpha particles are very efficient ICD initiators, i.e., create a strong low-energy electron yield in a regime in which continuum electrons are virtually nonexistent in ion-atom collisions.
In this talk, I will explain the main features and the limitations of our model,  provide an overview of the results obtained, and discuss their implications.

 
Vortex optique, moment orbital angulaire photonique et interaction avec les atomes
 
Mercredi 20 Avril 2022 à 14h Salle 101 de l’UFR de Chimie, couloir 32-42
 
Laurence Pruvost
 
Laboratoire A. Cotton, CNRS et Université de Paris-Saclay
 
Résumé:
Le vortex optique est un laser avec un front d'onde en hélice. Cette structure en vis sans fin, lui confère un moment orbital angulaire photonique (OAM) , une grandeur quantifiée aussi appelée le troisième moment du photon. Son échange avec la matière ouvre des questions liées à cette chiralité nouvelle et est étudiée notamment dans le cadre d'interactions non-linéaires.
Après une description de la technique de laser-shaping utilisée pour produire des lasers "singuliers" et des vortex optiques, on verra des applications notamment celle de l'interaction non-linéaire de l'OAM avec des atomes qui permet la conversion d'OAM, la génération de paires d'OAMs, mais aussi l'étude de systèmes quantiques via l'analogie  entre l'optique non-linéaire et l'équation de Schrödinger non-linéaire.
 
 

  

Microscopie électronique (STEM) sur échantillons minces et microanalyse X du lithium

 

Mardi 30 novembre 2021 à 14h Salle 101 de l’UFR de Chimie, couloir 32-42

Pr. Raynald GAUVIN

Department of Materials Engineering McGill University Montréal, Québec, Canada


 
Post Collision Interaction and photoelectron recapture in rare gases. Angular correlation, multi-step decay, and what not.
 
Jeudi 8 Octobre 2020 à 11h, salle 101, Département de Chimie, Tour 32-42
 
Yoshiro AZUMA 
Sophia University Tokyo and KEK, Photon Factory, Japan
 

Abstract:

We examine the atomic inner-shell photoionization process from above threshold, around threshold and below threshold, as the photoelectron-auger-electron dynamics transit from normal auger to PCI to photoelectron recapture to resonant auger in a seamless manner.  Clear cases transcending the conventional radial interaction model, exhibiting pronounced angular correlations are presented. Also, the inter-relation between the multi-steps via PCI raise new questions.


Light-induced electron dynamics in molecules by the time-dependent configuration interaction method

Mercredi 4 mars 2020 à 14h, salle 101, Département de Chimie, Tour 32-42

Pascal KRAUSE

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1D-14109 Berlin

Abstract:

In this talk, I would like to present a quantum theoretical method that is capable of monitoring the motion of electrons in molecules. The advances in computer technology made it possible to simulate the motion of electrons in molecules on their natural, attosecond time scale. I will discuss the possibility of controlling the electronic properties by means of the explicitly time-dependent configuration interaction (TDCI) method. Presented will be the scope of the method by the calculation of molecular electric response properties due to moderate laser fields as well as  angle-dependent ionization probabilities obtained by the inclusion of complex absorbing potentials (CAP). I will conclude with an outlook to my current project, the simulation of the Inter-Coulombic Decay (ICD) in a Germanium/Silicon core/shell nano crystal by means of the reduced density matrix variant of the TDCI method. The desired goal of this project will be the controlled transfer of electronic excitation between two nano crystals. 

 


 

CASTOR, un instrument de caractérisation de couches minces par XRR-GIXRF à SOLEIL

Mercredi 5 Février 2020 à 14h00, salle 101 du département de Chimie, Tour 32-42

 

Dr. Yves MENESGUEN

CEA-LIST – Centre de Saclay Laboratoire National Henri Becquerel

Résumé:

Le LNHB développe un instrument de caractérisation de films minces dans le cadre de ses activités de métrologie des rayons X. La technique hybride XRR-GIXRF combine la réflectivité aux rayons X (XRR) et la fluorescence X en incidence rasante (Grazing Incidence X-Ray Fluorescence). La réflectivité est plus sensible à la densité atomique numérique et la fluorescence à la nature des éléments. Ces deux techniques peuvent être employées séparément ou en combinaison pour améliorer la qualité du modèle et son ajustement aux mesures expérimentales. Le modèle d’empilement des couches prend en compte leur épaisseur, les rugosités aux interfaces, les mélanges d’éléments et leur interdiffusion éventuelle.


 

Electron Dynamics of Interatomic Coulombic Electron Capture in Artificial and Real Atoms

Vendredi  31 Janvier 2020 à 11h00, salle 101 du département de Chimie, Tour 32-42

 

Axel MOLLE

laboratoire de Chimie Physique Matière et rayonnement (LCPMR, SU, Paris)

Abstract

Interatomic coulombic electron capture is a non-local process involving the environment-assisted attachment of a free electron with implied consequences for various systems. It has been theoretically proposed by various methods to be involved to some extent in the biologically relevant system of a magnesium (II) cation in water [1], in the commercially important system of nanowire-embedded re-
gions of quantum confinement [2,3], and will be shown here to possibly play a role in the experimentally important system of trapped ions in ultracold atom clouds [4,5].
Therefore suggesting to be a universal process triggered by a free electron in a nearly arbitrary environment of atoms, this work reviews the established dynamical model for a nanowire-contained pair of quantum dots also known as artificial atoms [6], and presents the first numerical model to investigate ICEC dynamics of a barium (II) cation in a surrounding cloud of ultracold rubidium atoms at typical experimental conditions. While the first system may play a significant role in cutting edge computing technologies, the second offers the arguably most accessible blueprint to the first experimental proof of interatomic coulombic electron capture and explores the possibilities offered by current modular experiments of state-to-state chemistry.

[1] K. Gokhberg, and L. S. Cederbaum, J. Phys. B 42, 231001 (2009) 10.1088/0953-4075/42/23/ 231001.
[2] A. Molle, E. R. Berikaa, F. M. Pont, and A. Bande, Journal of Chemical Physics 150, 224105 (2019)[3] F. M. Pont, A. Bande, and L. S. Cederbaum, Phys. Rev. B 88, 241304(R) (2013) 10.1103/PhysRevB.88.241304.
[4] The Royal Swedish Academy of Sciences, The Nobel Prize in Physics 2001,
https://www.nobelprize.org/prizes/physics/2001/press-release/,
[5] The Royal Swedish Academy of Sciences, The Nobel Prize in Physics 1989,
https://www.nobelprize.org/prizes/physics/1989/press-release/,
[6] M. A. Kastner, ‘Artificial atoms’, Physics Today 46, 24–31 (1993) 10.1063/1.881393.


 

Multidimensional photon spectroscopy: Investigation of electronic processes

in atoms, molecules and clusters

Mercredi 22 janvier 2020 à 16h, salle 101 du département de Chimie, Tour 32-42

  Andreas Hans

Universität Kassel

Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel,Heinrich-Plett-Strasse 40, 34132 Kassel, Germany 

Résumé

Photon spectroscopy is a powerful method in atomic and molecular physics, allowing the identification and qualitative and quantitative characterization of a vast variety of decay mechanisms of excited quantum systems. The diverse capabilities of this method develop in multidimensional experiments, for example, if photon spectra are recorded in dependence of experimental parameters or in combination with other particles. In this seminar, I will give an overview of multidimensional photon-induced fluorescence spectroscopy. Here, synchrotron radiation is used for site- and state-selective electronic excitation of various targets and fluorescence spectroscopy is applied to investigate the subsequent relaxation. A particular focus will be the identification and characterization of non-local decay processes in weakly bound clusters. As an outlook, I will discuss the inclusion of photon detection in advanced experimental techniques like charged particle coincidence spectroscopy. 

 


 

Synthesis and Reactivity of Model catalysts, two examples: isolated Fe1O3 sites on Cu2O(100) and regular arrays of size controlled Pd clusters on an alumina thin film

Lundi 02 décembre 201 9à 14h00, Salle 101, Département de Chimie, Tour 32-42, 1er étage. 

Héloïse TISSOT

Centre Interdisciplinaire de Nanoscience de Marseille (CINAM)CNRS, Université d’Aix-Marseille

Résumé:

Controlling the morphology of the surface is of key importance for model catalysts in order to be able to identify active surface species and investigate how parameters (nanoparticle size, shape, composition, temperature, pressure, gasnature...) influence the surface reactivity. In this presentation, we will focus on CO oxidation on two systems, first on isolated Fe1O3 sites synthetized on Pt(111) and on Cu2O(100) surface and then on a regular array of Pd clusters on an alumina thin film on Ni3Al(111) exhibiting a size dispersion down to the ultimate limit of a Poisson distribution. These model catalysts were investigated by Scanning Tunneling Microscopy (STM) and their reactivity followed by NAP-XPS (Near Ambient Pressure-XPS) and MBRS (Molecular Beam Reactive Scattering).


 

Molecular Coulomb explosion and implosion, induced by free electron lasers

Lundi 25 Novembre 2019 à 14h00, Salle 101, Département de Chimie, Tour 32-42, 1er étage. 

Edwin KUKK

Dept of Physics and Astronomy, University of Turku, Finland

Résumé:

Photoinduced dynamics in small quantum systems has long fascinated physicists and chemists alike, both because of fundamental properties it reveals about the structure of matter, but also because it is a key element in many processes in biology and materials research. The introduction of free electron lasers about a decade ago, with its ultra-intense femtosecond pulses of light, promoted this research to a new level. Now, we can reconstruct the x-ray induced sequence of events in femto- and picosecond scale and obtain new insight into the interplay of nuclear and electronic dynamics.

The destructive properties of x-rays and UV light are well known; at the fundamental level they occur as photoinduced molecular dissociation and bond breakage (such as destruction of polymer chains). In biological organism, the most serious is such damage to the DNA molecules, that can lead to mutations and cancer. But, with the help of radiosensitizer molecules, this can also be turned to our advantage by helping to destroy cancerous cells.

Using the Japanese SACLA FEL, we have studied photoinduced dissociation processes in a number of organic compounds, often containing a heavy element (such as I or Br) as an absorption hot-spot. A review of those studies will be presented, interpreted with the aid of a parametric, simple Coulomb dynamics model that we developed for the purpose. We show, how the evolution of the dynamics csn be reconstructed from both pump-probe and also from a single-pulse experiment, using the complex information from multi-ion coincidence measurements. We show the importance of the charge creation dynamics and charge migration, and molecular vibrations. Also we show, how in specific situations the typical pattern of a violent Coulomb explosion of a highly charged system can change completely, into that of. Coulomb implosion, with very intricate trajectories and high sensitivity to initial conditions.


 

SYMPOSIUM ON MATTER-RADIATION IN EXTREME CONDITION 

Mercredi 17 Juillet 14h00-16h30,

Salle 101, Département de Chimie, Tour 32-42, 1er étage. 

Attoclock on Atomic and Molecular Hydrogen

Professor Anatoli Kheifets,

Research School of Physics, Australian National University, Canberra ACT 2601, Australia

 Controlling photoemission using electron wave-packets Interferences

Mathieu Gisselbrecht

Lund University, Lund, Suède.

Bichromatic ionization of atoms in XUV: Coherent control and around

A.N. Grum-Grzhimailo

Lomonosov Moscow State University, Russia.

 


 

Vibrational Intermolecular Coulombic Decay

Jeudi 20 Juin 2019 à 16h00, salle 101, Département de Chimie, Tour 32-42, 1er étage

Lorenz CEDERBAUM, Professeur

Theoretical Chemistry
Institute of Physical Chemistry,
University of Heidelberg
Im Neuenheimer Feld 229, 69120 Heidelberg, Germany

 

Résumé:

 Is an efficient intermolecular energy transfer from vibrations to electronic motion possible ? 

In this work we investigate the possibility of intermolecular vibrational energy transfer to electronic motion. Energy transfer of all kinds is of central importance for chemical reactivity and has been widely studied both experimentally and theoretically over many years including the transfer between the two kinds of energies, vibrational and electronic. The studies of the latter are, however, carried out in the framework of collisions where the collision complex formed and/or nonadiabatic coupling give rise to the transfer. Here, we concentrate on intermolecular vibrational energy transfer to electronic motion in weakly bound molecules, i.e., at internuclear distances at which they do not have a chemical bond and nonadiabatic coupling is negligible. We shall see that the transfer can be highly efficient. If time is left, intermolecular vibrational energy transfer between weakly bound molecules is also addressed. Here, most of the studies were done for describing resonant vibrational energy transfer in the condensed phase. Very recently, it has been noticed that if the lifetime of the vibrationally excited molecule is much longer than that of its neighbor, efficient non-resonant vibrational energy transfer can take place. 


 

K-edge resonances in Kr, Xe, and XeF2 using x-ray/ion coincidence spectroscopy

Mardi 18 Juin 2019 à 15h30, salle 101, Département de Chimie, Tour 32-42, 1er étage

Steve SOUTHWORTH

Argonne National LaboratoryUSA

Résumé:

The 1s-to-np Rydberg transitions below the 1s ionization thresholds of Kr and Xe are obscured in x-ray absorption spectra due to core-hole lifetime broadening. However, the np spectator electrons associated with those resonances can affect the core-hole decay spectra.  We observe variations of ion charge-state distributions of Kr and Xe  measured in coincidence with x-ray fluorescence as the incident x-ray energy is scanned through pre-edge resonances and ionization thresholds. The coincidence measurements select vacancy cascades that begin with a radiative transition that transfers 1s holes to the 2p, 3p, and 4p shells followed by emission of Auger electrons. High-level relativistic coupled-cluster calculations that treat relativistic, electron correlation, and wavefunction relaxation effects on the same footing obtain agreement with the experimental 1s ionization energies of Kr and Xe to less than 2 eV. Measurements were also made at the Xe K-edge of XeF2where excitation of the lowest unoccupied molecular orbital (LUMO) is observed.  Xe 1s core-hole decay in XeF2results in ionization of the F ligands and energetic fragmentation into atomic ions. For ion time-of-flight spectra recorded on the LUMO resonance, the F ion peaks are split into two peaks along the linear polarization direction of the incident x-ray beam.  This effect is attributed to spatial alignment of XeF2molecules by resonant x-ray absorption.  The peak splittings are used to measure the F ion fragmentation energies for three fluorescence pathways that leave the molecule in different outer-shell hole states.


 

Etats électroniques sur une surface “fractale“

Mardi 28 Mai 2019 à 14h30, salle 101, Département de Chimie, Tour 32-42, 1er étage

Alfred MAQUET

Professeur

Résumé:Pour la première fois, fin 2018, des chercheurs ont réussi à préparer un gaz d'électrons astreints à se déplacer sur une surface fractale de dimension non-entière. Le séminaire portera sur les propriétés du tapis de Sierpinski, sur les contributions de Jean Perrin sur le mouvement brownien (trajectoire fractale) ainsi que sur la préparation et l'étude de tels systèmes.


 Some recent advances in nanosciences seen through ab initio calculations

Mardi 21 Mai 2019 à 15h00, salle 101, Département de Chimie, Tour 32-42, 1er étage

Sébastien LEBEGUE 

Directeur de recherches CNRS 

Approche Multi-échelles des Milieux Complexes, Université de Lorraine, Laboratoire de Chimie et Physique , Nancy

In the field of nanosciences, research on materials has made spectacular progress over the last twenty years. In this talk, I will present, through some examples from recent works, how ab initio calculations can provide a better understanding of the physical and chemical properties of different compounds. In particular, I will discuss the physics of two-dimensional materials, surface physics, and zeolite-type molecular sieves. Finally, some current limits as well as future challenges for ab initio calculations will be described briefly. 

Quelques avancées récentes en nanosciences vues par le biais du calcul ab initio 

Dans le domaine des nanosciences, la recherche sur les matériaux a connue des progrès spectaculaires depuis une vingtaine d'années. Dans cet exposé, je présenterai, par l’intermédiaire de quelques exemples tirés de travaux récents, comment le calcul ab initio peut permettre d'obtenir une meilleure compréhension des propriétés physiques et chimiques de différents composés. En particulier, j'aborderai la physique des matériaux bidimensionnels, la physique des surfaces, et les tamis moléculaires de type zéolithe. Pour finir, les limites actuelles ainsi que les challenges à venir pour le calcul ab initio seront décrits succinctement. 


Pharmaceutical phase behaviour

Jeudi 11 Avril 2019 à 15h30, salle 101, Département de Chimie, Tour 32-42, 1er étage

Dr. Ivo RIETVELD

Laboratoire Sciences et Méthodes Séparatives, Université de Rouen Normandie Place Emile Blondel, 76821 Mont-Saint-Aignan CEDEX, France

Phase equilibria are considered a thing of the past since "Phase Theory" has been published by J.W. Gibbs 150 years ago. However, the richness in possibilities to control pharmaceutical formulations and on the other hand the delicate task of ensuring the stability of such formulations require a profound understanding of the phase behaviour of molecular compounds and of their interactions.

The presentation will highlight the importance of the solid state in close relationship to the liquid state in pharmaceutical applications. Examples will involve polymorphism, co-crystals, solubility, eutectics, miscibility gaps and racemic systems and their resolution.


Les actions de recherche soutenues par l'Agence Française pour la Biodiversité

Mardi 02 Avril 2019 à 14h00

Tour 22-23, 3ème étage, Salle 317, INSP 

Dr Pierre-François STAUB,

Agence Française pour la Biodiversité, Vincennes 


Towards non-linear X-ray spectroscopy for materials science with FELs

Dr. Martin BEYE
Deutsches Elektronen Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany

Ce séminaire aura lieu le Lundi 1er Avril  à 14h00 salle 101, Département de Chimie, Tour 32-42, 1er étage


A fully polarizable QM/MM approach for spectroscopies of aqueous solutions

Mercredi 6 mars 2019 à 15h00

Tour 24-34, 2e étage, salle 201

Dr. Alessandra PUGLISI

EmbedLab@SNS, Scuola Normale Superiore - Pisa (Italy)


Molecular Photoionization with Advanced Light Sources

Jeudi 21 Février 2019 à 14h30

ATTENTION Salle de séminaire inhabituelle :

Tour 24-34, 2e étage, salle 201

Dr Fabian HOLZMEIER, 

Dipartimento di Fisica, Politecnico di Milano, Italie fabian.holzmeier@polimi.it 

Significant progress in the development of versatile light sources in the VUV (vacuum ultraviolet) and X-ray energy range, i.e., the regime which leads to photoionization in molecules, has been achieved in the last two decades: Modern synchrotrons stand out featuring easy photon energy tunability and high spectral resolution, whereas a huge increase of the peak brilliance could be realized with free electron lasers (FELs). FELs provide also the possibility to perform time-resolved experiments with few tens of femtoseconds (fs) resolution [1]. On the other hand, the development of table-top laser high harmonic generation (HHG) sources yielding attosecond pulses in the XUV (extreme ultraviolet) and soft X-ray range provide the prospect to study molecular photoionization phenomena with an unprecedented time-resolution without the need for access of large-scale facilities [2].

In this seminar, selected examples of recent experiments on the photoionization of small molecules in the gas phase with synchrotron radiation, FEL pulses, and ultrashort HHG pulses will be discussed. The first part will focus on high-resolution Auger spectra of isocyanic acid HNCO, a molecule of high importance in combustion and interstellar chemistry, recorded at the soft X-ray beamline at Synchrotron SOLEIL (Paris, France) [3]. In the second part, a study on the control of the dissociative photoionization of the benchmark molecule H2with intense VUV femtosecond pulses provided by the Fermi FEL (Trieste, Italy) is presented [4]. Finally, a brief outlook on molecular photoionization experiments with attosecond pulses will be given, highlighted by preliminary results from experiments at the ATTOLab facility (Paris, France). These examples will showcase how experiments with synchrotrons, FELs and HHG sources can complement one another in order to obtain a deep insight into molecular photoionization processes and dynamics.

References

[1] L. Young et al.J. Phys. B: At. Mol. Opt. Phys. 51, 032003 (2018).

[2] M. Nisoli, P. Decleva, F. Calegari, A. Palacios, F. Martín, Chem. Rev.16, 117 (2017).

[2] F. Holzmeier et al.“Normal and resonant Auger spectroscopy of HNCO”, J. Chem. Phys. 149, 034308 (2018).

[3] F. Holzmeier et al.“Control of H2Dissociatve Using FEL Pulses”, Phys. Rev. Lett. 121, 103002 (2018).


Experimental and theoretical studies of core shell excited or ionized Argon

Jeudi 7 Février 2019 à 14h30 salle de séminaire de l'Institut des Nano Sciences de Paris (INSP), Tour 22-23, 3ème étage, salle 317

Dr. Saana-Maija HUTTULA, Nano and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland

Abstract:

The Nanomo group at the University of Oulu has a long history in the research of gases and vapors using electron spectroscopy. The group has done pioneering research especially in the field of synchrotron radiation physics. The research on atomic physics targets on the inner and core shell photoexcitation and related processes. The experimental techniques range from conventional electron spectroscopy carried out using hemispherical analyzers to photoelectron-photoion spectroscopy and many-electron coincidence measurements using magnetic-bottle time-of-flight devices.

The Nanomo unit focuses strongly in theoretical understanding of the studied processes. For small systems, atomic and molecular simulations are carried out starting from the first principles utilizing the latest quantum mechanical frameworks and programs. Multiconfiguration Dirac-Fock and Hartree-Fock theories are used to obtain transition energies, transition probabilities and angular distributions of Auger and photoelectrons. As an example, some studies of Auger and cascade Auger processes following Ar 2p-14s excitation, Ar+2p, Ar 2s and K 2s ionization are given.

S.-M. Huttula, et al. Phys. Rev. Lett. 110, 113002 (2013)

Lablanquie et al.Phys. Chem. Chem. Phys.13, 18355 (2011)

Fritzsche, et al. Phys. Rev. A 75, 012501 (2007)

S.-M. Huttula et al.Phys. Rev. A 63, 032703 (2001)


Quantum optics and Interatomic Coulombic Decay: Connections, limitations and new possibilities

Lundi 11 Février 2019 à 16h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

Dr. Robert BENNETT,
Dept. of Physics, Univ. of Crete, Heraklion, 70013, Greece 

Albert-Ludwigs-Universität Freiburg Physikalisches Institut Hermann-Herder-Str. 3 79104 Freiburg Germany 

Abstract: Interatomic Coulombic decay (ICD) is an ultrafast process by which energy can be transferred among atoms and molecules. Usually the process is described in ab initio quantum chemistry, which works very well at short distances and without external environments. Borrowing techniques from quantum optics and Casimir physics, we recently put forward an alternative `virtual photon’-based model which can deal with the effects of relativistic retardation and those of external environments [1]. In this talk I will briefly introduce ICD and its importance, describe our new model and present some very recent results for three-body ICD [2] 
 
[1] J. L. Hemmerich, R. Bennett, and S. Y. Buhmann, Nat. Commun. 9, 2934 (2018).
[2]R. Bennett, P. Votavová, P. Kolorenč, T. Miteva, N. Sisourat, and S. Y. Buhmann, ArXiv quant-Ph 1811.09489 (2018).
 

Studying chemistry processes with nitrogen K-edge XAS and RIXS combining experimental data with (TD)DFT calculations

Dr. Pieter MIEDENA
Dept. of Physics, Univ. of Crete, Heraklion, 70013, Greece

Ce séminaire aura lieu le Jeudi 13 Décembre 2018 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Two-center electron-electron interactions revisited: Going beyond the electron scattering model using multi-electron close-coupling calculations in fast ion-atom collisions

Pr. Theo J.M. ZOUROS
DESY Hambourg

Ce séminaire aura lieu le Jeudi 28 Janvier 2018 à 14h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Electron spectroscopy of isolated atoms and molecules using soft and hard X-ray synchrotron radiation

Dr Ralph PÜTTNER
Institut für Experimentalphysik, Freie Universität Berlin, Germany 

Ce séminaire aura lieu le Lundi 26 Novembre 2018 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Dynamique de fragmentation d'agrégats de gaz rares chargés dans des nanogouttes d'hélium : application à Arn+He1000.

Dr David BONHOMMEAU
Groupe de Spectrométrie Moléculaire et Atmosphérique (GSMA), UMR CNRS 7331, Université de Reims Champagne-Ardenne

Ce séminaire aura lieu le Vendredi 5 Octobre 2018  à 11h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


De la mission spatiale Rosetta à BepiColombo : utilisation et besoin des sections efficaces de collisions dans les missions d’exploration planétaire.

Dr Pierre HENRI
Laboratoire de Physique et Chimie de l’Environnement et de l’Espace(LPC2E), UMR 7328 du CNRS, Orléans

Ce séminaire aura lieu le Vendredi 5 Octobre 2018  à 11h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Opportunities for x-ray scattering and x-ray spectroscopy studies at the SCS instrument at the European XFEL

Dr Justine SCHLAPPA
European XFEL, Hambourg

Ce séminaire aura lieu le Mardi 19 Juin 2018 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Materials analysis and modification using MeV heavy ions?

Dr Iva RADOVIC
Institut Rudjer Boskovic à Zagreb, Croatie

Ce séminaire aura lieu le Vendredi 13 Avril 2018 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Introduction à la cinétique des gaz

Romain JARRIER
LCPMR

Ce séminaire aura lieu le Mardi 13 Mars 2018 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Attosecond-resolved photoionization of chiral molecules

Samuel BEAULIEU
CELIA, Université de Bordeaux & INRS-EMT (Canada)

Ce séminaire aura lieu le Mercredi 17 Janvier 2018 à 14h30 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Attosecond metrology of partially coherent electron wavepackets

Charles BOURASSIN-BOUCHET
Institut d'optique, Palaiseau

Ce séminaire aura lieu le Jeudi 30 Novembre 2017 à 15h30 salle 101, Département de Chimie, Tour 32-42, 1er étage



New trends in 'complete' experiment on atomic photoionization and time evolution of atomic K-holes 

Pr Alexei GRUM-GRZHIMAILO
Moscow Univiversity Russia

Ce séminaire aura lieu le Lundi 27 Novembre 2017 à 14h30 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


ICD and ETMD in Noble Gas Clusters

Dr Elke FABHAUER
Dept of chemistry, Univ. of Copenhagen, Denmark

Ce séminaire aura lieu le Mardi 3 Octobre 2017 à 15h00 salle 509, LLPP/LERMA, Tour  24-34, 5ème étage.

 


Theoretical approaches for time-resolved experiments using attosecond and femtosecond x-ray pulses

Dr Antonio PICON ALVAREZ
Universidad de Salamanca & Institut de Ciències Fotòniques, ICFO, Spain

Ce séminaire aura lieu le Mardi 4 Juillet 2017 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Tracking electron dynamics in graphene and transition metal dichalcogenides

Dr Céphise CACHO
Artemis Central Laser Facility, Rutherford Appleton Laboratory, United Kingdom

Ce séminaire aura lieu le Mercredi 21 Juin 2017 à 15h salle 101, Département de Chimie, Tour 32-42, 1er étage

 


La vie dans l'univers: où la vie peut-elle se développer sur une exoplanète?

Pr Alfred MAQUET
LCPMR

Ce séminaire aura lieu le Mardi 21 Mars 2017 à 15h00 salle 101, Département de Chimie, Tour 32-42, 1er étage

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Castor, un nouvel outil pour l'analyse combinée XRR-GIXRF

Dr Anastasia NOVIKOVA
Laboratoire National Henri Becquerel, Gif/Yvette

Ce séminaire aura lieu le Mardi 14 Mars 2017 prochain à 15h30 salle 101, Département de Chimie, Tour 32-42, 1er étage

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New Tools for investigating Ultrafast Dynamics in Biologically relevant molecules

Dr Raluca CIREASA
Institut des sciences moléculaires Université Paris Sud, Orsay

Ce séminaire aura lieu le Jeudi 23 Février 2017 à 16h salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Absorption of ultrafast and intense x rays by nitrogen molecules 

Pr. Christian BUTH
Heidelberg University, Germany

Ce séminaire aura lieu le Mercredi 22 Février 2017 à 16h salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Le moment angulaire de la lumière en génération d'harmoniques d'ordres élevés

Dr Romain GENEAUX
Attolab, CEA Saclay

Ce séminaire aura lieu le Mardi 25 Janvier 2017 à 15h salle 101, Département de Chimie, Tour 32-42, 1er étage

 


Cinétique Atomique et interaction XFEL-matière

Dr Olivier PEYRUSSE
Lab. de Physique des interactions Ioniques et moléculaires PIIM, UMR 7345 Aix-Marseille Université

Ce séminaire aura lieu le Mardi 17 Janvier 2017 à 14h salle 101, Département de Chimie, Tour 32-42, 1er étage


Présentation du logiciel de conception CATIA et les avancées sur le logiciel de simulation numérique COMSOL Multiphysics 

Romain JARRIER 
LCPMR

Ce séminaire aura lieu le Mardi 10 Janvier 2017 à 15h salle 101, Département de Chimie, Tour 32-42, 1er étage


Nano and molecular systems unit at the University of Oulu

Dr Kari JÄNKÄLÄ 
Nano and Molecular Systems Research Unit, Oulu, Finlande

Ce séminaire aura lieu le Vendredi 4 Novembre 2017 à 15h salle 317, INSP, Tour 22-23, 3ème étage



Présentation de l'OEB (office européen des brevets) et du système du brevet européen

Dr Michael BOROWSKI
European Synchrotron Radiation Facility, Grenoble et Bureau des Brevets Européens, Munich.

Ce séminaire aura lieu le Mardi 7 Juin 2016 à 16h, Amphithéâtre Jean Perrin


Dynamique attoseconde de photoionisation

Dr Matthieu GISSELBRECHT
Dpt physique, Université de Lund, Suède

Ce séminaire aura lieu le Mardi 3 Mai 2016 à 16h, Amphithéâtre Jean Perrin



Nonlinear Acousto-Magneto Plasmonics

Dr Vasily TEMNOV
Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, Université du Maine, 72085 Le Mans, France.

Ce séminaire aura lieu le Mardi 12 Avril 2016 à 16h, Amphithéâtre Jean Perrin



Conception et caractérisation de matériaux en couches minces pour l'ophtalmique

Tito de AYGUAVIVES, Pierre­‐Jean CALBA, Hélène MAURY, Delphine POINOT
ESSILOR International - Centre de Recherche et Développement, Créteil

Ce séminaire aura lieu le Mardi 23 février 2016 à 15h30, Amphithéâtre Jean Perrin

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Excitation of vibrational modes in the ionization of water molecule by XUV/X-ray radiation

Dr. Selma ENGIN
Universitad Autonoma Madrid, Esapgne.

Ce séminaire aura lieu le Mercredi 2 Décembre 2015 à 16h15, Amphithéâtre Jean Perrin



X-ray Spectroscopic Methods for structure and dynamics of the interfaces of (oxide) nanolayers study

Elena FILATOVA
Professeur invité de l'IP2CT et du LCPMR

Ce séminaire aura lieu Lundi 30 Novembre 2015 à 15h30, Amphithéâtre Jean Perrin

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Rôle des alcalins sur les interfaces des cellules solaires à base de Cu(In,Ga)Se2

Dr. Sylvie HAREL
Université de Nantes

Ce séminaire aura lieu le Mardi 26 Mai 2015 à 15h30, Amphithéâtre Jean Perrin

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Photo-induced ultrafast nuclear dynamics in core-excited molecules

Oksana TRAVNIKOVA (nouvellement nommé Chargée de Recherche au LCPMR)
Tongji University, Shanghai, China

Ce séminaire aura lieu le Vendredi 17 Avril 2015, à 15h, Amphithéâtre Jean Perrin.

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Contrôle de l'organisation de molécules et de nanoparticules d'or sur silicium pour l'électronique moléculaire

Olivier PLUCHERY
INSP

Ce séminaire aura lieu le Mardi 14 Avril 2015, à 16h, Amphithéâtre Jean Perrin

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Development of the X-­‐ray Timing and Polarization telescope optics

Pr. Zhanshan WANG
Tongji University, Shanghai, China

Ce séminaire aura lieu le Mardi 27 fevrier 2015, 15h30, Amphithéâtre Jean Perrin.

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Post-Collision-Interaction In Processes of Inner Shells Photoionization

Professeur Sergei Sheinerman
Université de St Petersbourg

Ce séminaire aura lieu le Mardi 27 janvier 2015, 16h00, Amphithéâtre Jean Perrin.

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Interface engineering methods for multilayer optics in the EUV, soft X-ray and X-ray ranges

Prof. Jingtao ZHU
Key Laboratory of Advanced Micro-structured Materials of Ministry of Education, School of Physics Science and Engineering
Tongji University, Shanghai 200092, China

Ce séminaire aura lieu le Mardi 24 juin 2014 à 15h30, Amphithéâtre Jean Perrin.

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Multilayer optics for applications in the EUV, x-­ray and gamma­‐ray ranges

Regina SOUFLI
Lawrence Livermore National Laboratory
Livermore, California, USA

Ce séminaire aura lieu le Mardi 10 juin 2014 à 15h30, Amphithéâtre Jean Perrin

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Reflectivite Magnetique Resonante de rayons X: vers une application pompe-sonde pour une resolution spatiale et temporelle ?

Emmanuelle JAL
Stanford Institute for Materials Energy Sciences SLAC National Accelerator
Laboratory, 2575 Sand Hill Road CA 94025 Menlo Park

Ce séminaire aura lieu Mercredi 21 Mai 2014 à 15h00, Amphithéâtre Jean Perrin

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