Letteratura scientifica selezionata sul tema "Spectroscopie par ionisation laser résonante"
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Tesi sul tema "Spectroscopie par ionisation laser résonante"
Sifi, Rosa. "Ionisation résonante par faisceaux laser : Application aux sources d'ions et à l'étude de la structure des noyaux radioactifs de tellure". Phd thesis, Université Paris Sud - Paris XI, 2007. http://tel.archives-ouvertes.fr/tel-00252001.
Testo completoLa naissance du projet ALTO (Accélérateur Linéaire auprès du Tandem d'Orsay) à l'IPN d'Orsay a fait émerger l'idée d'installer une source d'ions laser. A cet effet, une étude de faisabilité a été entreprise avec une installation laser à faible cadence (30 Hz) celle-ci devant être étendue à 20 kHz sur la future installation de faisceaux radioactifs (ALTO). Après un premier faisceau d'étain ionisé avec succès par cette source, nous avons poursuivi l'étude avec un faisceau de cuivre. Nous avons d'abord effectué des tests de schémas d'ionisation du cuivre stable : un schéma vers le continuum et deux schémas vers des états autoionisants voisins. Le schéma le plus efficace commence par une étape d'excitation de longueur d'onde λ1 = 249.2 nm suivie d'une longueur d'onde d'ionisation λ2 = 439.92 nm. Celle-ci correspond à un état autoionisant situé à 62845 cm-1 non connu auparavant et voisin des deux autres états autoionisants sélectionnés au départ. L'efficacité d'ionisation laser avec ce schéma a été mesurée et elle est semblable à celle prédite par la théorie.
L'ionisation résonante par faisceaux laser est également utilisée dans des expériences de spectroscopie auprès de COMPLIS à ISOLDE au CERN. La technique dans ce cas consiste à effectuer un balayage en fréquence autour de la transition d'excitation des atomes pour sonder leur structure hyperfine. Cette étape sera suivie de l'étape d'ionisation pour ioniser les atomes et les détecter. La spectroscopie laser nous permet de déterminer la structure hyperfine et le déplacement isotopique des atomes. Nous avons utilisé cette technique pour étudier les isotopes de tellure sur une longue chaîne isotopique 125m, 127mg, 129mg, 131mg, 132, 133mg, 134, 135 et 136Te. A partir des déplacements isotopiques mesurés nous avons déterminé la variation du rayon carré moyen de charge qui fait apparaître une rupture de pente du rayon de charge à N = 82 : la déformation du noyau diminue jusqu'à N = 82 où elle atteint la sphéricité puis elle augmente au-delà.
La mesure de la structure hyperfine des isotopes impairs de tellure nous a permis de déterminer les constantes de structure hyperfine des isotopes 135 et 133 dans leur état fondamental (Iπ = 7/2- et 3/2+ respectivement) et des isotopes 125, 127, 129, 131 et 133 dans leur état isomérique (Iπ = 11/2-). A partir de ces constantes nous avons extrait les moments nucléaires : µI et Qs. La comparaison des valeurs des moments magnétiques µI expérimentales avec les valeurs de moments existantes dans la littérature mesurées par résonance magnétique nucléaire nous donne un parfait accord.
L'extraction des valeurs des déformations à partir des moments quadrupolaires spectroscopiques en supposant une symétrie axiale conduit à une quasi sphéricité pour tous ces noyaux. Malgré les grandes barres d'erreurs, elles sont semblables aux valeurs des moments quadrupolaires des isotopes d'étain.
Ajayakumar, Anjali. "In gas jet laser spectroscopy optimization for high resolution measurement of actinides". Electronic Thesis or Diss., Normandie, 2023. http://www.theses.fr/2023NORMC267.
Testo completoThe Super Separator Spectrometer-Low Energy Branch (S3-LEB) is a low-energy radioactive ion beam experimental setup under commissioning as part of the GANIL-SPIRAL2 facility. In this thesis work, the off-line commissioning of the S3-LEB setup, including first laser spectroscopy measurements in both the gas cell and the supersonic gas jet, the determination of the transport efficiency of laser ions from the gas cell through the RFQ chain, and time-of-flight measurements with the multi-reflection time-of-flight mass spectrometer PILGRIM are discussed. The measurements were performed using erbium, introduced by evaporation from a heated filament in the gas environment. The reported laser spectroscopy results include a characterization of the pressure broadening in the gas cell and proof-of principle isotope shift and hyperfine-structure measurements. This work proves the potential of the setup to conduct the future online tests, where erbium is chosen as the first case for online commissioning. Offline laser ionization and spectroscopy of uranium and americium from the actinide series have been discussed. This thesis work also includes technical developments such as the implementation of the titanium sapphire laser systems and a dedicated entrance window test bench for the S3-LEB. A continuous wave diode-pumped laser system has been built for high-resolution laser spectroscopy application. Americium laser spectroscopy measurements at RISIKO present the potential of such a laser system in performing high-resolution measurements in actinides
Mahjoub, Ahmed. "PROCESSUS ÉNANTIOSÉLÉCTIFS DANS DES COMPLEXES À LIAISONS HYDROGÈNE". Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00459590.
Testo completoManuelli, Pascal. "Etude des mécanismes de la désorption : ionisation laser assistée par matrice". Metz, 1995. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1995/Manuelli.Pascal.SMZ9520.pdf.
Testo completoThis report on the mechanisms of matrix assisted laser desorption ionization (MALDI) was realized in mass spectrometry laboratory at Metz'university. This research field appeared in the laboratory after the development of biomolecules analyses by mass spectrometry and the experience stored for fifteen years on "laser desorption". We decomposed the different states of a MALDI experiment for a better understanding of this ionization process. By using some model compounds (as peptides, nucleotides,. . . ) we have studied more precisely the interaction between a laser beam and the different matrices. This allow us to show the great role of small neutral molecules (e. G. Carbone dioxide,. . . ) which are ejected in the plume after the laser pulse. Then, some derivative and complexes of cyclodextrins have been studied. This part is necessary to explain first the interaction between matrix and target molecules and secondly the dependance on the laser wavelength. Thank's to the MALDI technique we can highlight both both structural differences in intact inclusion complexes characterization
Verdun, Francis. "Analyses des hydrocarbures aromatiques polycycliques in situ et étude de l'ionisation en phase solide avec effets de résonance par microsonde laser lamma". Metz, 1985. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1985/Verdun.Francis.SMZ8507.pdf.
Testo completoLengignon, Christophe. "Développement d'un système de mesure de radicaux hydroxyles par spectroscopie d'absorption en cavité résonante hors axe". Phd thesis, Université du Littoral Côte d'Opale, 2012. http://tel.archives-ouvertes.fr/tel-00874400.
Testo completoFerré, Amelie. "Etude des dynamiques moléculaires sondées par générations d'harmoniques d'ordres élevés". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0165/document.
Testo completoHigh harmonic generation (HHG) spectroscopy has proven to be a promisingtool (like probe in pump-probe experiments) in revealing the atomic and molecular dynamicswith the potential for subangstrom spatial resolution and subfemtosecond temporalresolution. Then, rotational dynamics have been resolved on small molecular systems (N2,CO2). This thesis looks to extending HHG spectroscopy methods to probe the structureand the dynamic of complex molecular systems. We will describe the two sources highharmonic generation, the transient grating of excitation and the two-color high harmonicgeneration. We enable to resolve the femtosecond nuclear dynamics in N2O4 and SF6. HHGis also used like a XUV radiation source, playing the role of pump pulse. This approach hasbeen used for the study of photoelectron circular dichroism. An XUV harmonic field witha quasi-circular polarization ionizes chiral molecules. In this manuscript, we will developthis new femtosecond XUV and quasi circular polarization radiation
Henares, González Jose. "Study of condensable ion production by resonant laser ionization". Caen, 2016. http://hal.in2p3.fr/tel-01314260.
Testo completoThis doctoral thesis describes the development of a Resonant Ionization Laser Ion Source (RILIS) at the GANIL facility. The RILIS is a selective ion source technique which is based on a step-wise resonant excitation process where the elements of interest are ionized via atomic resonant excitation by laser radiation. The off-line RILIS test bench at GANIL consists of three tunable titanium:sapphire lasers and a hot-cavity ion source. In this thesis, a new three-step Zn ionization scheme was developed and the already known ionization schemes for Sn have been compared in order to identify the best ionization scheme for titanium:sapphire laser systems. Furthermore, several configurations of the ion source geometry were tested (two diameters and two lengths) in order to provide an optimal ionization efficiency and ion beam emittance. An increasing of the ionizer diameter was found to enhance the production of laser ionizer elements, while no enhancement was observed by modifying the ionizer length. The time-of-flight of the generated ions was also studied for the different ion source configurations at several temperatures. The time-of-flight can provide information about the ion formation inside the ion source cavity. In addition, a technique to measure the convolution of the spatial and energetic spread of the ion bunches at the detection point was developed. Finally, two contamination reduction techniques were studied: Firstly, the ions trajectories through the ion source cavity can be modified by the electric field generated due to resistive heating. Therefore, a study of the appropriate configuration of the electric field direction was performed to reduce the alkali contamination of the ion beam. Secondly, a low work function material was tested in order to reduce the production of alkali contaminants and molecular sidebands generated inside the ion source
Shenar, Nawar. "Spectrométrie de masse par désorption/ionisation laser de peptides modèles : applications en protéomique". Montpellier 2, 2008. http://www.theses.fr/2008MON20150.
Testo completoMasselon, Christophe. "Etude des mécanismes d'ablation-ionisation laser de pesticides adsorbés sur membranes par spectrométrie de masse à transformée de Fourier". Metz, 1997. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1997/Masselon.Christophe.SMZ9712.pdf.
Testo completoLaser desorption/ionisation coupled with Fourier transform mass spectrometry is an ever growing technique with promising applications in the field of surface analysis. However, this method is very sensitive to the experimental parameters. Through this work, after having defined the physical phenomena invoked in the process, we have put the stress on the practical implications of the microscopic processes which have to be taken into account during the analysis. Several examples illustrate this demonstration. The feasability of the method for the analysis of pesticides adsorbed on solid phase extraction membranes has been evaluated for the first time. Five compounds with very different structures and various applications in agriculture have been analysed by classical mass spectrometry and their fragmentation products have been compared to those obtained by laser desorption at 248 nm wavelength. The analysis of the membrane by laser desorption has allowed us to evaluate the possible interferences and the ablation depth at various irradiances. The experiments concerning atrazine and its metabolite have allowed us to propose two distinct ionisation mecanisms : gas phase ionisation versus "true" desorption. Moreover, at the 248 nm wevelength, the various compounds adsorbed on membranes have shown very different behaviors which are better explained by their respective octanol/water partition coefficient than by their absorbance at the laser wavelength. The use of a tripled Nd-YAG laser has allowed the detection of the compounds which couldn't be detected at 248 nm and to confirm the hypothesis of a deeper adsorption of these compounds into the membrane