May 2016
Visiting researcher from China (IMP): Dong Bin Qian (2 months)
Dr. Dong Bin Qiang is working on ns-LASER induced ioniaztion and dissociation of C70 cations.
Visiting researcher from Japan (IMP): Jun Matsumoto (2 months)
Dr. Jun Matsumoto is collaborating on experiments with the Mini-Ring. He is studying the cooling and reheating processes of Naphtalene cations on 1 to 100 millisecond timescales using several ns-LASER impulsions during a single storage sequence in the Mini-Ring.
November 2015
Fast radiative cooling of anthracene: Dependence on internal energy
Published in Physical Review A (Phys. Rev. A, 2015, 92, 053425)
Abstract:
Fast radiative cooling of anthracene cations (C14H10)+ is studied with a compact electrostatic storage device, the Mini-Ring. The time evolution of the internal energy distribution of the stored ions is probed in a time range from 3 to 7 ms using laser-induced dissociation with 3.49-eV photons. The population decay rate due to radiative emission is measured to vary from 25 to 450s-1 as a function of the excitation energy in the range from 6 to 7.4 eV. After corrections of the infrared emission effect via vibrational transitions, the fluorescence emission rate due to electronic transitions from thermally excited electronic states is estimated and compared with a statistical molecular approach. In the considered internal energy range, the radiative cooling process is found to be dominated by the electronic transition, in good agreement with our previous work [S. Martin et al., Phys. Rev. Lett. 110, 063003 (2013)] focused on a narrower energy range.
September 2015
Installation and test of the COMIC ECR ion source from Polygon Physics.
July 2015
XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC) was held in Toledo, Spain on 22 –28 July 2015
Poster presentations:
- “Dissociation rate, fluorescence and Infrared radiative cooling rates of Naphthalene studied in electrostatic storage Miniring”
- “Singlet and triplet states dissociation of doubly charged HDO, H2O and D2O as a function of internal energy”
- “Dissociation of doubly charged Coronene as a function of internal energy”
Molecular Physics Workshop, Caen, 7-10 July 2015 - Université de Caen Basse-Normandie, France
Invited talk: "Dissociation and radiative cooling of PAH ions as a function of internal energy" (R. Brédy)
June 2015
Thursday, June 25th 2015 , 10:00 AM amphithéâtre de Physique Nucléaire, Bâtiment Paul Dirac
Titre en français: "Dynamique de refroidissement du cation Naphtalène dans un anneau de stockage électrostatique"
English title: "Cooling dynamics of Naphthalene cations studied in an electrostatic storage ring"
Abstract:
L’étude des Hydrocarbures Aromatiques Polycycliques (PAH) a connu un intérêt croissant depuis une trentaine d’années, notamment à cause de leur éventuelle responsabilité dans l’émission de bandes infrarouges encore non attribuées du milieu interstellaire. Les études en laboratoire des mécanismes de refroidissement de ces molécules isolées sont alors primordiales pour accroitre les connaissances actuelles sur le temps de vie et la taille critique de ces molécules dans les nuages interstellaires. Le développement dès les années 1990 de dispositifs de piégeage entièrement électrostatiques a permis une avancée considérable sur la compréhension de la dynamique de relaxation sur des temps longs, de la nanoseconde à quelques secondes, de petites et de grosses molécules comme les PAH.
Dans ce travail de thèse, la dynamique de refroidissement du cation naphtalène C10H8+, la plus petite molécule de la famille des PAH, est étudiée dans un anneau de stockage électrostatique, le Mini-Ring. Les processus de refroidissement par dissociation et par émission de photons sont les deux voies de relaxation majoritaires du C10H8+ étudiés dans la thèse.
Les cations naphtalène sont créés dans une source à résonance cyclotronique, accélérés à 12 keV et stockés pendant plusieurs millisecondes dans le Mini-Ring. La dynamique de refroidissement des cations est étudiée en enregistrant, en fonction du temps de stockage, le nombre de neutres émis suite à la dissociation des ions. Ce nombre de neutres est mesuré avec un détecteur sensible en temps et en position. Le processus de photo-dissociation induit par une excitation laser de longueur d’onde 532 nm, est utilisée pour sonder la distribution en énergie interne des ions stockés à différents temps de stockage. Ces distributions sont déterminées en analysant les courbes de déclin à l’aide d’un programme numérique développé pendant la thèse. L’évolution temporelle de la distribution en énergie interne des ions met en évidence un processus de refroidissement rapide caractérisé par un taux de refroidissement compris entre 70 et 90 s-1 pour des énergies internes de 5.9 et 6.8 eV. Ce refroidissement rapide ne peut être expliqué par l’émission de photons infrarouges. Il est attribué à la « fluorescence de Poincaré » caractérisée par un processus de conversion interne inverse suivie de l’émission d’un photon dans le domaine du visible. Cette fluorescence de Poincaré ou fluorescence récurrente a été prédite il y a plus de 20 ans mais n’a jamais été mesurée précisément à ce jour.
June 8-11: 6th International Workshop on Electrostatic Storage Devices (ESD 2015) was held at Tokyo Metropolitan University and RIKEN, Japan
Invited talk: "The cooling of PAHs cations studied in the Mini-Ring" (C. Ortéga)
Poster présentation: “Fluorescence and infrared radiative cooling rates of naphthalene studied in electrostatic storage Mini-Ring”
SIMION Users Meeting at GANIL (France)
Invited talk: “Ion trajectory simulations for the design of a compact electrostatic ion storage ring: the Mini-Ring” (J. Bernard)
Mai 2015
Visiting researcher from China (IMP): Dong Bin Qian (2 weeks)
April 2015
Tuesday, April 28th 2015 , 10:00 AM amphithéâtre de Physique Nucléaire, Bâtiment Paul Dirac
Titre en français: "Dynamique de relaxation de cations d'Anthracène étudiée dans un anneau de stockage électrostatique"
English title: "Molecular Relaxation Dynamics Of Anthracene Cations Studied In An Electrostatic Storage Ring"
Abstract:
The polycyclic aromatic hydrocarbon (PAH) molecules have been considered as possible carrier of the unidentified infrared emission bands from the interstellar medium (ISM) for about thirty years. The cooling dynamics of PAH molecules which is essential to estimate their photostability and therefore their lifetime and size distributions in the ISM, has attracted numerous theoretical and experimental studies. In recent years, electrostatic storage devices (ESD) became powerful tool to investigate the cooling regime of molecules and clusters in a large time range from microseconds to seconds. Generally speaking, the decay of the emitted neutral yields due to dissociation of molecular cations or electron detachment of anions in such experiments carries information on the internal energy of the stored molecular ions.
In this thesis work, the cooling of anthracene cations has been studied in a compact electrostatic storage ring, the Mini-Ring up to 8 ms. A spontaneous neutral yield curve obtained from the stored molecular ions as function of storage time shows three distinguishing regions. The three regions indicate different cooling regimes at corresponding storage time range, i.e., dissociation dominates at storage time t < 1 ms, quenching occurs during 1 < t < 3 ms and radiative cooling governs at t > 3 ms.
During the storage cycle, laser pulses are optional to be sent to irradiate stored molecular ions at well-controlled storage time. The laser induced neutral yield curves are fitted with law, and the decrease of a with storage time indicates the shift of the internal energy distribution (IED) of stored ions to lower energies. Combining with a simple modeling of the a-IED dependence, the high energy edge of IED and the shift rate of IED as well, are estimated at various storage times. By changing the photon energy ( to ) of laser pulses to irradiate the stored ions, two series of a are obtained. The time interval necessary for the IED of stored ions to undergo a shift that matches the energy difference of are determined as a function of storage time, thus the shift rate of IED is estimated without involving any IED simulations.
The radiative cooling of anthracene cation is also studied at long storage time range t > 3 ms. By fitting the laser induced experimental neutral yield curves with theoretical ones calculated from the modeled dissociation rates and assumed multi-parameter function to estimate the IED, the IED of the stored ions is drawn up. The average energy shift rate of IED from 3 to 7 ms is estimated to be about 100 eV s-1. The population decay of IED due to radiative emission is measured to be 25 to 450 s-1 as function of internal energy from 6 to 7.4 eV. After the correction of the effect due to infrared emission via vibrational transitions, the fluorescence emission rate due to electronic transitions from thermally excited states is obtained. In the studied internal energy range, the electronic transition is the dominant process in the radiative cooling.
March 2015
Fragmentation of doubly charged HDO, H2O, and D2O molecules induced by proton and monocharged fluorine beam impact at 3 keV
Published in The Journal of Chemical Physics (Chem. Phys. 142, 094306 (2015) )
Abstract:
Doubly charged ions HDO2+, H2O2+, and D2O2+ were prepared selectively to triplet or singlet excited states in collisions with F+ or H+ projectiles at 3 keV. Excitation energies of dications following two-body or three-body dissociation channels were measured and compared with recent calculations using ab initio multi-reference configuration interaction method [Gervais et al., J. Chem. Phys. 131, 024302 (2009)]. For HDO2+, preferential cleavage of O–H rather than O–D bond has been observed and the ratio between the populations of the fragmentation channels OD+_H+ and OH+_D+ were measured. The kinetic energy release has been measured and compared with previous experiments.
January 2015
ILM evaluation by HCERES (Haut Conseil de l'évaluation de la recherche et de l'enseignement supérieur)
December 2014
Visiting researcher: Géraldine FERAUD (PIIM: Laboratoire de Physique des Interactions Ioniques et Moléculaires)
October 2014-Januray 2015
Visiting researchers from Japan: Naoko Kouno (3 months) and H. Tanuma (1 week)
Mini-Ring experiments with PAHs (naphthalene)
May 2014
Front cover of AstroPAH newsletter
Fall 2013-Spring 2014
Renovation of the experimental rooms
March 2013
The article Fast Radiative Cooling of Anthracene Observed in a Compact Electrostatic Storage Ring published in Physical Review Letters was highligthed in the actualities of Institut de Physique of CNRS (in French only)
Actualités scientifiques du CNRS: Etudier en laboratoire les grains interstellaires grâce à un anneau de stockage électrostatique
L'article intitulé Fast Radiative Cooling of Anthracene Observed in a Compact Electrostatic Storage Ring publié dans la revue Physical Review Letters fait l'objet d'une actualité de l’institut de Physique du CNRS.
Résumé: Des physiciens ont développé un anneau de stockage électrostatique, dont la taille n’est que de quelques dizaines de centimètres, afin d’étudier en laboratoire les propriétés des grains interstellaires ou de grosses molécules carbonées. Ce dispositif permet de conserver ces particules assez longtemps pour reproduire les conditions extrêmes de vide et de basse température qui règnent dans les milieux astrophysiques. (lire la suite, site du CNRS)
November 2010
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4 years funding from ANR Blanc 2010–042601 "ANNEAU" Dynamique de fragmentation de molécules étudiée avec un anneau électrostatique Fragmentation dynamics of molecules studied using an electrostatic ring |
December 4th 2007
CIDEC highlight in Liberation by AZAR KHALATBARI: Espace vital
October 2007
CIDEC highlight in Le courrier du CNRS n°213 oct. 2007: Un nouvel outil pour découper les molécules and Futura science