Séminaires

Jeudi 18 Mai 2017 à 14H00
Amphithéâtre MREI1
« Applications of rotational spectroscopy to molecular biology and to astrochemistry »
Dr Celina BERMUDEZ,
post-doctorante au PhLAM à Lille
The applications of the rotational spectroscopy have been expanded to different scientific domains during the last decades. Two of them are molecular biology and astrochemistry. The combination of laser ablation and broadband and narrowband Fourier transform microwave spectroscopy in supersonic jets allows to unveil for the first time the intrinsic conformational and tautomeric behavior of small biological molecules such as amino acids, sugars or neurotransmitters. This knowledge, for instance, could help to establish new theories of the molecular recognition of sweeteners (how we taste the sweetness) or to find the role of the amino acids in proteins. In the field of astrochemistry, the rotational spectroscopy is constituted as an empirical support of the detection of molecules in the interstellar medium (ISM). It allows to identify in the ISM: new molecules; vibrational excited states of the already detected ones, which will to provide information of the environment of their location; unstable species, which help us to understand the chemistry of the universe, or molecules of large amplitude motions of complex spectroscopy.

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Vendredi 12 Mai 2017 à 14H00
Amphithéâtre MREI1
« Spectroscopie à haute résolution de molécules organiques d’intérêt astrophysique et atmosphérique contenant des mouvements de grande amplitude »
et
« La spectroscopie infrarouge haute résolution en jet supersonique : structure et dynamique rovibrationnelle dans les molécules et les complexes moléculaires »
Atef Jabri et Pierre Asselin,
du laboratoire MONARIS (de la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies), UMR CNRS / Université Pierre et Marie Curie (UPMC, Paris 6)
Résumé 1 : La spectroscopie de rotation permet de déduire des informations cruciales quant à la structure et aux propriétés des composés. Certaines molécules organiques peuvent avoir des mouvements de grande amplitude comme la rotation interne d’un groupe d’atomes (le groupe méthyle CH 3 par exemple). Un tel mouvement est un phénomène de non-rigidité moléculaire qui nécessite une approche théorique spécifique.
Les molécules de thioformate de méthyle (CH3SCH(O) et CH3OCH(S)) et de sulfure de diméthyle (CH3)2S présentent un intérêt à la fois astrophysique car elles sont potentiellement détectables dans le milieu interstellaire (MIS) mais aussi un intérêt pour l’étude de l’atmosphère terrestre. Pour ce faire, nous avons effectué pour la première fois une étude spectroscopique complète au laboratoire pour ces molécules en vue d’étudier leurs spectres de rotation dans les régions spectrales des microondes (2-40 GHz), millimétriques (150-660 GHz) et infrarouge (150-220 cm -1 et 963-987 cm -1 ).
L’analyse spectrale complète pour ces molécules sera présentée en détaillant toutes les approches théoriques utilisées.

Résumé 2 : Depuis une trentaine d’années, l’association entre la technique de jet supersonique et les méthodes spectroscopiques d’absorption infrarouge à haute résolution (interférométrie, laser) s’est avérée indispensable pour caractériser la structure rovibrationnelle de systèmes moléculaires stables de masse élevée, mais aussi de complexes moléculaires faiblement liés, dans un environnement gazeux sans collisions à très basse température [1,2]. MONARIS est impliqué dans le développement de deux montages pour élargir le champ d’investigation de la spectroscopie rovibrationnelle en phase gazeuse : (i) le montage Jet-AILES (consortium IPR-PhLAM-MONARIS) implanté sur la ligne AILES du synchrotron SOLEIL, un jet libre continu couplé à un spectromètre IR à transformée de Fourier haute résolution, (ii) le montage SPIRALES, implanté à MONARIS, un jet pulsé couplé à un spectromètre laser accordable autour de 6 et 10 µm.
Dans cet exposé, je présenterai les caractéristiques, les performances et la complémentarité entre ces 2 montages. Des exemples récents d’études (ro)vibrationnelles de complexes moléculaires et de molécules lourdes seront présentés pour illustrer les potentialités de ces plateformes spectroscopiques [3-6].

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Mercredi 1er Mars 2017 à 14H30
Amphithéâtre MREI1
« A new method for CH3O2 and C2H5O2 radical detection and kinetic studies of the CH3O2 and C2H5O2 self-reactions in HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) »
Dr Laviania Onel,
from University of Leeds, School of Chemistry
Peroxy (RO2) radicals such as methyl peroxy (CH3O2) and ethyl peroxy (C2H5O2) are significant atmospheric species in the ozone formation in the presence of NO. At low concentrations of NO, the self-reaction of RO2 and RO2 + HO2 are important radical termination. Despite their importance, at present typically only the sum of RO2 radicals is measured in the atmosphere, making no distinction between different RO2 species.
This talk will describe a new method for the selective detection of CH3O2 and C2H5O2 by FAGE (Fluorescence Assay by Gas Expansion) by titrating CH3O2 and C2H5O2, respectively to RO (R = CH3 and C2H5) by reaction with NO and then detecting the resultant RO by off-resonant laser induced fluorescence. The method has the potential to directly measure atmospheric levels of CH3O2. The use of the new method in kinetic studies performed in the atmospheric simulation chamber HIRAC will be presented. The talk will then move to the observation of reaction products in HIRAC by using multi-pass FTIR.

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Mardi 28 Février 2017 à 14H30
Amphithéâtre MREI1
« Laser sources for spectrometric applications »
Dr Dominique Mammez,
laboratoire FOTON de Lannion (CNRS / Université de Rennes)
Spectrometry takes a growing part in dealing with environmental problematics (atmospheric studies, detection and monitoring of pollutants and molecules of atmospheric interest, safety of industrial sites by chemical leakage checking, etc.) as it enables nondestructive precise and real-time measurements. In most spectrometers, the light source is a key element affecting the resolution, accuracy and detection limit of the system. Similarly, the emission range of the source determines the type of molecules that can be addressed by the spectrometer. Thus, each application will induce constraints concerning the source, in terms of power, stability, robustness, tuning range and emission linewidth.
The work presented during this seminar concerns the development, frequency control, characterization and implementation of infrared sources mainly for the measurement of atmospheric gas. In the first place, I will expose my PhD work on the realization and the implementation of mid-infrared external cavity – quantum cascade laser (EC-QCL) performed at the GSMA (CNRS UMR 7331). Then I will present the frequency control and characterization of a near-infrared optical parametric oscillator (OPO) source for LIDAR DIAL applications, work carried out at ONERA, the French Aerospace Lab. Eventually I will present current developments on blue lasers implemented at FOTON Laboratory (CNRS UMR 6082) for Raman spectrometric application in marine environment.

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Jeudi 23 Février 2017 à 11H00
Amphithéâtre MREI1
« Studies of OH and HO2 by FAGE (Fluorescence Assay by Gas Expansion) and HO2 by cw-CRDS (continuous wave-Cavity Ring Down Spectroscopy) »
Dr Marion Bloquet,
from Jülich Forschungszentrum (Germany)
OH and HO2 radicals are major reactive species in many environments and the chemical processes in which they are involved are numerous and complex. In the atmosphere, OH is the main oxidant during the day and HO2 is strongly linked to it. OH has also been measured recently in indoor air; highlighting the presence of a rapid reactivity and therefore a potential source of secondary pollutants in buildings. In combustion, OH and HO2 are also important for the reactivity. To better understand chemical processes involving these radicals and consequently the formation of pollutants in these fields of application, the mobile device FAGE (Fluorescence Assay by Gas Expansion) of Lille has been used in these environments: atmosphere (on the field or in atmospheric chamber), indoor air and combustion. This technique allows characterizing OH and HO2 by combining concentration and lifetime (OH reactivity) measurements with a high sensitivity, selectivity and temporal resolution. It is based on the detection of OH and HO2 radicals by Laser Induced Fluorescence (LIF) at a high repetition after gas expansion. It is adapted for OH reactivity measurements by the coupling of a photolysis cell (pump-probe FAGE). A field campaign, performed on the Lille 1 campus, allowed the study of the variation of the reactivity in an urban environment. An intercomparison of the OH reactivity in the SAPHIR chamber (Jülich, Germany) allowed the comparison of 2 techniques and 9 instruments. Two field campaigns were performed in indoor air to both measure OH reactivity and quantify OH and HO2; a third measurement cell has been developed for these simultaneous measurements. The FAGE device was also used for the first time in the field of combustion chemistry, by coupling it to a Jet-Stirred Reactor (JSR). A new cw-CRDS (continuous wave-Cavity Ring Down Spectroscopy) instrument is developed to measure HO2 radicals in the SAPHIR chamber with a high sensitivity. This technique consists in measuring the time of exponential decay of the light intensity stored in a resonant cavity, in order to deduce its absorption by the molecules present. The cw-CRDS and FAGE of Jülich measurements will be compared in the future.

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Lundi 30 Janvier 2017 à 14H30
Amphithéâtre MREI1
« Segmented Chirped Pulse Fourier Transform Millimeter Wave Spectroscopy and Its Analytical Applications »
Dr Amanda Steber,
from Hamburg University
Chirped pulse Fourier transform spectroscopy is a sensitive, broadband technique that relies on fast digital electronics. This technique allows the user to measure phase coherent spectra of greater than 10 GHz for the analysis of complex molecular systems. It was first used in microwave spectroscopy in 2006[1], but then was extended to the millimeter wave (mm-wave) regime in 2012 at the University of Virginia[2] after solid-state mm-wave-to-THz sources became available. The instrument presented here relies on these active multiplier chains (AMCs) to up-convert phase stable microwave pulses that are generated from arbitrary waveform generators (AWGs) to mm-wave frequencies, between 260-295 GHz. After the pulses are broadcast across the chamber, where they interact with a room-temperature sample, the free induction decay of the molecular sample is collected and down-converted to the microwave regime so that fast digital electronics can be used to digitize the time domain signal. In order to circumvent the need for high priced oscilloscopes the segmented chirped pulse method[3] was employed. In this approach, the total bandwidth of the instrument is broken into several segments. This increases the time required to acquire the entire spectrum while simultaneously decreasing the required number of averages needed to attain a specified dynamic range, thus making it analogous to the full band procedure. The instrument was fully automated using Python, and it was tested to determine the sensitivity limits on both single samples, as well as gas mixtures. Results of these sensitivity measurements will be presented.
[1] G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, B.H. Pate, J. Mol. Spectrosc. 238 (2006) 200–212.
[2] A.L. Steber, B.J. Harris, J.L. Neill, B.H. Pate, J. Mol. Spectrosc. 280 (2012) 3–10.
[3] J.L. Neill, B.J. Harris, A.L. Steber, K.O. Douglass, D.F. Plusquellic, B.H. Pate, Opt. Express 21 (2013) 19743–19749.

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Jeudi 12 Janvier 2017 à 10H30
Visio-conférence Amphithéâtre MREI1
« On the advantage of coupling different diagnostics for a more complete characterization of soot particles »
Dr. Jérome Yon,
Maître de conférence au COmplexe de Recherche Interprofessionnel en Aérothermochimie (CORIA) de Rouen
Dans cette présentation, l’accent est porté sur la détermination de l’indice optique des particules de suie. L’indice optique est une donnée d’entrée essentielle pour la plupart des techniques optiques de mesure de caractéristiques de suies (taille, morphologie, concentration) mais qui souffre d’une méconnaissance encore importante. Par ailleurs, les propriétés optiques des suies sont également un indicateur de la composition chimique et de la structure atomique de ces particules. Au travers de cette présentation, nous montrerons que la détermination fine de l’indice optique des particules de suie nécessite le développement de modèles d’interaction lumière-particules adaptés, une caractérisation morphologique avancée des agrégats de suie, une interprétation des mesures granulométriques conventionnelles (SMPS) et un couplage de techniques non optiques afin de déterminer la masse volumique de la suie. La démarche proposée qui repose sur un couplage de techniques différentes vise à fournir une caractérisation la plus complète possible des particules de suie.

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Mardi 6 Décembre 2016 à 15H30
Amphithéâtre Extension de la Citadelle à Dunkerque.
« TCCON-Paris, le 1er site TCCON dans une mégacité européenne »
Dr Yao TE,
Maître de conférence à l’Université Pierre et Marie Curie (Paris 6) au sein du Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères (LERMA)
Durant son intervention, il présentera le spectromètre à transformée de Fourier installé sur le campus de Jussieu et les activités de recherche menées autour de cet instrument concernant entre autres la variabilité et les tendances des polluants atmosphériques, la validation des instruments satellitaires, l’analyse de paramètres spectroscopiques, l’acquisition de spectres de laboratoire pour les espèces d’intérêt atmosphérique… See PDF

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Lundi 21 Novembre 2016 à 10H00
en visio-conférence, au CERLA à Lille, et dans l’amphithéâtre de la Citadelle à Dunkerque.
Séminaire II
« Using precision spectroscopy of diatomic molecules to investigate fundamental physics: 207Pb19F hyperfine splittings »
Professeur Trevor SEARS,
Professeur au Départment de Chimie de Stony Brook University, NY, et Senior Chemist à Brookhaven National Laboratory, NY
Recently, it has been realized that precision measurements of the spectra of certain small molecules containing a heavy atom can provide opportunities to investigate parity-violating effects and other fundamental interactions. This is because electrons in the molecules experience relativistic forces in the regions of their wavefunction that overlap the heavy nucleus. Examples include the recent upper-limit determination for the electron dipole moment and recent searches for nuclear anapole moments. One molecule that has received attention as a possible candidate for study of these effects is PbF and this lecture will build on the material in the earlier lectures and cover some aspects of the spectroscopy of the ground state that makes it attractive for these studies. See PDF

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Jeudi 10 Novembre 2016 à 14H00
en visio-conférence, au CERLA à Lille, et dans l’amphithéâtre de la Citadelle à Dunkerque.
Séminaire I
« Old problems meet new techniques: Applications of frequency comb-referenced spectroscopy »
Professeur Trevor SEARS,
Professeur au Départment de Chimie de Stony Brook University, NY, et Senior Chemist à Brookhaven National Laboratory, NY
Frequency comb technology has become widely available and relatively inexpensive, so that it is now practical to routinely measure optical spectra with accuracy and precision approaching a few parts in 1012. This is some 4 orders of magnitude greater than can be achieved with wavelength- based measurement techniques. It opens up possibilities for the measurement of precise spectral splittings and line positions for fundamental spectroscopy, but also dramatically improves the accuracy with which we can measure spectral line shapes. Line shapes contain information on collisional processes within the sample and intermolecular potentials. Their knowledge is also centrally important in practical remote sensing measurements. In this talk, I will outline the frequency comb idea and spectroscopic techniques and illustrate the kinds on data attainable with examples from line shape and frequency measurements in the molecules C2H2 and NH3. See PDF

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8, 9, 15 et 16 Novembre 2016 à 8H30
en visio-conférence, dans le Bâtiment de Physique P5 (salle 172) à Lille 1, et en salle de visio de l’ULCO (Citadelle) à Dunkerque
Série de 4 cours
« Angular momentum, symmetry and rotational energy levels »
Professeur Trevor SEARS,
Professeur au Départment de Chimie de Stony Brook University, NY, et Senior Chemist à Brookhaven National Laboratory, NY
These lectures will begin with a review of the matrix approach to the eigenvalue problem using the hyperfine structure of the hydrogen atom as an example. Then cover some details of angular momentum operators, spherical tensor formalism and Wigner-Eckart theorem. By the end, students should be familiar with methods to calculate matrix elements of different fine and hyperfine contributions to the molecular Hamiltonian. The final seminar will focus on use of the methods to compute the different energy contributions to the hyperfine split levels of 207Pb19F in its zero point level which is relevant to investigations of parity-violating effects. See PDF

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Mercredi 14 septembre 2016 à 10h00
Amphithéâtre MREI 1
« ESSENS: Chinese Earth Simulator Facility ? an IAP project in next five years »
Professeur Hongbin CHEN,
de l’Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS)
Earth system is composed of 5 main components including the atmosphere, ocean, lithosphere, cryosphere, and biosphere. Nowadays, the anthropogenic activities have significant effects on global environmental change. In order to tackle the science problems of the earth system, to predict the Earth future evolution, and to find new ways for global sustainable development, an Earth simulator is essentially required to reproduce and predict all principal processes in the Earth system and the interactions between all components. In the next 5 years, a big project called ‘Earth System SciencE Numerical Simulator facility (ESSENS)’ will be conducted by CAS/IAP in collaboration with tens of partners.

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lundi 12 septembre 2016 à 10h30
Amphithéâtre MREI 1
« Topological ordering in structurally disordered material »
Professeur Takeshi USUKI,
de l’Université de Yamagata (Department of Material and Biological Chemistry)
The structural investigation of glasses and liquids remains an interesting challenge in the science of disordered materials. Experimental techniques such as neutron and X-ray scattering methods that provide a variety of information on a wide range of length scales are therefore necessary to fully understand their unique properties. The local structure and intermediate range ordering in bulk metallic glasses and fast ionic conductive glasses are investigated in detail using a combination of experimental and computational modelling tools, such as the reverse Monte Carlo method. The analysis of all results reinforce evidence for the characteristic ordering in the systems, and suggests that atomic arrangements are considered to have a very important role for their unique properties. The nature and interplay between the ordering on the nearest-neighbour and intermediate length scales will be characterised and discussed.