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1. Laser-Induced Electron Diffraction in Chiral Molecules

Author

Debobrata Rajak, Sandra Beauvarlet, Omer Kneller, Antoine Comby, Raluca Cireasa, Dominique Descamps, Baptiste Fabre, Jimena D. Gorfinkiel, Julien Higuet, Stéphane Petit, Shaked Rozen, Hartmut Ruf, Nicolas Thiré, Valérie Blanchet, Nirit Dudovich, Bernard Pons, and Yann Mairesse

Subjects
Physics, QC1-999
Abstract

Strong laser pulses enable probing molecules with their own electrons. The oscillating electric field tears electrons off a molecule, accelerates them, and drives them back toward their parent ion within a few femtoseconds. The electrons are then diffracted by the molecular potential, encoding its structure and dynamics with angstrom and attosecond resolutions. Using elliptically polarized laser pulses, we show that laser-induced electron diffraction is sensitive to the chirality of the target. The field selectively ionizes molecules of a given orientation and drives the electrons along different sets of trajectories, leading them to recollide from different directions. Depending on the handedness of the molecule, the electrons are preferentially diffracted forward or backward along the light propagation axis. This asymmetry, reaching several percent, can be reversed for electrons recolliding from two ends of the molecule. The chiral sensitivity of laser-induced electron diffraction opens a new path to resolve ultrafast chiral dynamics.

Published
2024
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2. Attosecond processes and X-ray spectroscopy: general discussion

Author

Daniel Rolles, Ágnes Vibók, Fernando Martín, Christopher J. Milne, Albert Stolow, Martin Centurion, Kiyoshi Ueda, Dave Townsend, Sebastian Mai, Adam Kirrander, Oliver Schalk, Shaul Mukamel, Morgane Vacher, Dane R. Austin, Misha Ivanov, Hans Jakob Wörner, Peter M. Weber, Jonathan P. Marangos, Victor Kimberg, Michael P. Minitti, Artem Rudenko, Jan Marcus Dahlström, R. J. Dwayne Miller, Zdenek Masin, Markus Kowalewski, Allan S. Johnson, Ruaridh Forbes, Alvaro Sanchez-Gonzalez, Nirit Dudovich, Danielle Dowek, Daniel M. Neumark, Filippo Bencivenga, Raluca Cireasa, Wolfgang Domcke, and Imperial College London

Subjects
X-ray spectroscopy, Materials science, Attosecond, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry, Atomic physics, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016
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3. Shaping electron-hole trajectories for solid-state high harmonic generation control

Author

Michael Krüger, Barry D. Bruner, Sagie Gadasi, Raluca Cireasa, Ayelet Julie Uzan, Nirit Dudovich, Gal Orenstein, and Talya Arusi-Parpar

Subjects
Physics, 0303 health sciences, Field (physics), business.industry, Attosecond, Second-harmonic generation, Laser, 01 natural sciences, Atomic and Molecular Physics, and Optics, law.invention, 03 medical and health sciences, Optics, law, Harmonics, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Harmonic, High harmonic generation, Waveform, 010306 general physics, business, 030304 developmental biology
Abstract

Solid-state high-harmonic generation (HHG) by an intense infra-red (IR) laser field offers a new route to generate coherent attosecond light pulses in the extreme ultraviolet regime. The propagation of the IR driving field in the dense solid medium is accompanied by non-linear processes which shape the generating waveform. In this work, we introduce a monolithic scheme in which we both exploit the non-linear propagation to manipulate a two color driving field, as well as generate high harmonics within a single crystal. We show that the resulting non-commensurate, bi-chromatic, generating field provides precise control over the periodicity of the HHG process. This control enables us to manipulate the spectral positions of the discrete harmonic peaks. Our method advances solid-state HHG spectroscopy, and offers a simple route towards tunable, robust XUV sources.

Published
2019
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4. Electronic and non-adiabatic dynamics: general discussion

Author

Filippo Bencivenga, Peter M. Weber, R. J. Dwayne Miller, Kyoung Koo Baeck, Hans Jakob Wörner, Kiyoshi Ueda, Albert Stolow, Raluca Cireasa, Oliver Gessner, Jonathan P. Marangos, Maxim F. Gelin, Michael A. Robb, Fernando Martín, Álvaro Jiménez-Galán, Oliver Schalk, Simon P. Neville, Wolfgang Domcke, Jan R. R. Verlet, Russell S. Minns, Pankaj Kumar Mishra, Gareth Roberts, Markus Kowalewski, Dave Townsend, Piero Decleva, Allan S. Johnson, Thomas J. Penfold, Shaul Mukamel, Michael P. Minitti, Theis I. Sølling, Adam Kirrander, Iakov Polyak, Morgane Vacher, Dmitrii V. Shalashilin, Taro Sekikawa, Andrew J. Orr-Ewing, Danielle Dowek, Daniel M. Neumark, Dmitry V. Makhov, and Imperial College London

Subjects
Materials science, Classical mechanics, Dynamics (mechanics), [CHIM]Chemical Sciences, 02 engineering and technology, Physical and Theoretical Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, 0210 nano-technology, Adiabatic process, 01 natural sciences, ComputingMilieux_MISCELLANEOUS, 0104 chemical sciences
Abstract

International audience

Published
2016
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5. Using high harmonic radiation to reveal the ultrafast dynamics of radiosensitiser molecules

Author

Valérie Blanchet, Dominique Descamps, Stéphane Petit, Yann Mairesse, Raluca Cireasa, Pierre Çarçabal, Interactions Ions-Matière (LCAR) (I²M), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), Femto (LCAR), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), and Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Valence (chemistry), Chemistry, [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Ion, Extreme ultraviolet, Radiation damage, High harmonic generation, Molecule, Physical and Theoretical Chemistry, Atomic physics, Rydberg state, 0210 nano-technology, Ultrashort pulse
Abstract

International audience; 5-Fluorouracil (5FU) is a radiosensitiser molecule routinely used in combined chemo-and radio-therapies to enhance and localize cancer treatments. We have employed ultra-short XUV pulses produced by high harmonic generation (HHG) as a pump pulse to study the dynamics underlying the photo-stability and the radiation damage of this molecule. This work shows that it is possible to resolve individual dynamics even when using unselected HH. By comparing the results with those obtained in the multiphoton absorption at 400 nm, we were able to identify the frequencies of the HH comb relevant to the recorded dynamics: HH5 and HH3. The latter excites a high-lying Rydberg state interacting with a valence state and its dynamics is revealed by a 30 fs decay signal in the parent ion transient. Our results suggest that the same photoprotection mechanisms as those conferring photostability to the neutral nucleobases and to the DNA appear to be activated: HH5 excites the molecule to a state around 10.5 eV that undergoes an ultrafast relaxation on a timescale of 30 fs due to nonadiabatic interactions. This is followed sequentially by a 2.3 ps internal conversion as revealed by the dynamics observed for another fragment ion. These dynamics are extracted from the fragment ion signals. Proton or hydrogen transfer processes are required for the formation of three fragments and we speculate that the time scale of one of the processes is revealed by a H+ transient signal.

Published
2016
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6. Probing molecular chirality on a sub-femtosecond timescale

Author

A. F. Alharbi, M. C. H. Wong, A. E. Boguslavskiy, Dominique Descamps, Stéphane Petit, J. Suarez, A. Ferré, Bruno E. Schmidt, Serguei Patchkovskii, François Légaré, Nicolas Thiré, Bernard Pons, Yann Mairesse, Olga Smirnova, Valérie Blanchet, H. Ruf, Raluca Cireasa, V. R. Bhardwaj, J. Higuet, Baptiste Fabre, Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), National Research Council of Canada (NRC), University of Ottawa [Ottawa], Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), Advanced Laser Light Source-INRS-EMT, Énergie Matériaux Télécommunications - INRS (EMT-INRS), Institut National de la Recherche Scientifique [Québec] (INRS)-Université du Québec à Montréal = University of Québec in Montréal (UQAM)-Institut National de la Recherche Scientifique [Québec] (INRS)-Université du Québec à Montréal = University of Québec in Montréal (UQAM), Femto (LCAR), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Departamento de Química, C-9, Universidad Autónoma de Madrid, Universidad Autonoma de Madrid (UAM), King Abdulaziz City for Science and Technology (KACST), King Abdulaziz City for Science and Technology, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Universidad Autónoma de Madrid (UAM)

Subjects
Physics, [PHYS]Physics [physics], chemical physics, Enantioselective synthesis, ultrafast photonics, General Physics and Astronomy, Nanotechnology, Spectral line, Orders of magnitude (time), Chemical physics, Femtosecond, Molecule, High harmonic generation, high-harmonic generation, Enantiomer, Chirality (chemistry)
Abstract

Molecules that are mirror images of each other usually behave identically, unless they are interacting with other chiral objects. High-harmonic generation can provide access to the dynamics of chiral interactions on ultrafast timescales. Chiral molecules that are non-superimposable mirror images of each other, known as enantiomers, have identical chemical and physical properties unless they interact with another chiral entity, such as chiral light. Chiroptical1 effects arising from such interactions are used to detect enantiomers in mixtures and to induce enantioselective synthesis and catalysis. Chiroptical effects often arise from the interplay between light-induced electric- and magnetic-dipole transitions in a molecule and evolve on ultrafast electronic timescales. Here we use high-harmonic generation2,3 from a randomly oriented gas of molecules subjected to an intense laser field, to probe chiral interactions on these sub-femtosecond timescales. We show that a slight disparity in the laser-driven electron dynamics in the two enantiomers is recorded and amplified by several orders of magnitude in the harmonic spectra. Our work shows that chiroptical detection can go beyond detecting chiral structure4,5,6,7 to resolving and controlling chiral dynamics on electronic timescales.

Published
2015
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7. Influence of the surface treatment of the substrate in the LCVD of CNx films

Author

Rodica Alexandrescu, F. Vasiliu, A. Andrei, I. Morjan, V. Nelea, Raluca Cireasa, Aurelian Crunteanu, and Ion N. Mihailescu

Subjects
Materials science, Scanning electron microscope, technology, industry, and agriculture, Analytical chemistry, Surfaces and Interfaces, General Chemistry, Substrate (electronics), Chemical vapor deposition, Condensed Matter Physics, Surfaces, Coatings and Films, chemistry.chemical_compound, chemistry, Electron diffraction, X-ray photoelectron spectroscopy, Materials Chemistry, Crystallite, Thin film, Carbon nitride
Abstract

Carbon nitride (CNx films have been prepared by UV (at 248 nm) laser-induced chemical vapor deposition using different materials (alumina, laser-activated alumina, pre-deposited Ti layers on alumina, sapphire and quartz) as deposition substrates. A mixture of ethylene, nitrous oxide and ammonia was chosen as the gas-phase precursor. The changes induced in the gas-phase composition by the irradiation in different experimental conditions were determined by IR transmission measurements. The film composition and morphology were studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron diffraction (TED). The degree of chemical content modification, especially its dependence on the nature of the substrate, is described for the first time. Depending on the substrate nature, the specific nucleation and growth morphology of crystallites were observed. The electron diffraction data agree well with experimental results obtained in previous works and theoretical data referring to crystalline α- and β-C3N4 phases.

Published
1998
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8. CNx thin films obtained by laser induced CVD in different gas–substrate systems

Author

Rodica Alexandrescu, G. Pugna, I. Morjan, Raluca Cireasa, S. Petcu, Aurelian Crunteanu, Ion N. Mihailescu, and A. Andrei

Subjects
Materials science, General Physics and Astronomy, chemistry.chemical_element, Mineralogy, Surfaces and Interfaces, General Chemistry, Substrate (electronics), Condensed Matter Physics, Laser, Surfaces, Coatings and Films, law.invention, Carbon film, chemistry, X-ray photoelectron spectroscopy, Chemical engineering, law, Thin film, Carbon, Deposition (law), Titanium
Abstract

The possibility to deposit CN x thin films by laser-induced CVD technique was investigated. For this purpose, different carbon/nitrogen containing mixtures and substrates were used. CO 2 and the KrF laser irradiations were employed. The deposition was alternatively performed on laser pre-deposited catalytic titanium thin films and on bare substrates (quartz and alumina). An XPS analysis of CN x film composition reveals that in the presence of Ti layers nitrogen incorporation is enhanced and chemical structures with higher transfer states are favored.

Published
1997
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9. An experimental study on iron thin films obtained by laser pyrolysis of iron pentacarbonyl vapour

Author

Raluca Cireasa, Rodica Alexandrescu, I. Morjan, Ion N. Voicu, and G. Pugna

Subjects
Co2 laser, Materials science, Analytical chemistry, chemistry.chemical_element, Surfaces and Interfaces, General Chemistry, Condensed Matter Physics, Laser, Surfaces, Coatings and Films, law.invention, Iron pentacarbonyl, chemistry.chemical_compound, Carbon film, chemistry, law, Materials Chemistry, Laser pyrolysis, Thin film, Carbon, Quartz
Abstract

The results of a study on laser-assisted CVD of iron thin films from Fe(CO)5 vapour using a CO2 laser are presented. The iron-based layers deposited onto quartz substrates were characterised by different analytical techniques, and the influence of the precursor pressure and laser incident energy on the physical and chemical properties of films was pointed out. It was deduced that the purity of the as-deposited films depends on the different phases of carbon incorporation, which in turn is strongly influenced by the dynamics of the prevaling gas-phase processes.

Published
1996
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10. Inhomogeneous high harmonic generation in krypton clusters

Author

C. Handschin, Nicolas Thiré, Raluca Cireasa, A. Ferré, Eric Constant, Eric Mével, H. Ruf, Stéphane Petit, Dominique Descamps, Baptiste Fabre, Yann Mairesse, Valérie Blanchet, Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), Femto (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), European Project: 37686,MOLCOTUV, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
FOS: Physical sciences, General Physics and Astronomy, chemistry.chemical_element, PACS: 42.65.Ky, 32.80.Rm, 36.40.Vz, 01 natural sciences, law.invention, 010309 optics, Frequency conversion, Harmonic response, law, 0103 physical sciences, High harmonic generation, Physics - Atomic and Molecular Clusters, High order, 010306 general physics, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Physics, Spatially resolved, Krypton, Frequency mixing, [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], Laser, Computational physics, chemistry, Atomic physics, Atomic and Molecular Clusters (physics.atm-clus)
Abstract

High order harmonic generation from clusters is a controversial topic: conflicting theories exist, with different explanations for similar experimental observations. From an experimental point of view, separating the contributions from monomers and clusters is challenging. By performing a spectrally and spatially resolved study in a controlled mixture of clusters and monomers, we are able to isolate a region of the spectrum where the emission purely originates from clusters. Surpringly, the emission from clusters is depolarized, which is the signature of statistical inhomogeneous emission from a low-density source. The harmonic response to laser ellipticity shows that this generation is produced by a new recollisional mechanism, which opens the way to future theoretical studies., Comment: accepted at Physical Review Letters

Published
2013
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11. Probing chiral molecules by high harmonic generation

Author

A. F. Alharbi, Stéphane Petit, Micheal Wong, Yann Mairesse, Serguei Patchkovskii, Ravi-Bhardwaj Vedula, Nicholas Thire, Bruno E. Schmidt, Baptiste Fabre, Raluca Cireasa, Bernard Pons, François Légaré, J. Surarez, H. Ruf, Andrey E. Boguslavskiy, Dominique Descamps, and Valarie Blanchet

Subjects
Physics, Infrared, High Energy Physics::Lattice, High Energy Physics::Phenomenology, Electron, Laser, Molecular physics, law.invention, Magnetic field, law, Extreme ultraviolet, Quantum mechanics, High harmonic generation, Molecule, Physics::Atomic Physics, Chirality (chemistry)
Abstract

We introduce High Harmonic Generation (HHG) as a new molecular chirality probe. Chiral sensitivity arises from non-planarity of electron trajectories in the continuum due to the influence of magnetic field of the laser.

Published
2013
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12. High-harmonic transient grating spectroscopy of NO2 electronic relaxation

Author

C. Handschin, Paul B. Corkum, Valérie Blanchet, Dominique Descamps, Raluca Cireasa, H. Ruf, Laurent Bonnet, Nicolas Thiré, Philippe Halvick, Stéphane Petit, A. Ferré, David Staedter, J. B. Bertrand, David M. Villeneuve, E. Mével, Pascal Larrégaray, Yann Mairesse, Eric Constant, Baptiste Fabre, Bernard Pons, Hans Jakob Wörner, Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), Femto (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Natl Res Council Canada, Laboratoire de Physico-Chimie Moléculaire (LPCM), Université Sciences et Technologies - Bordeaux 1-Centre National de la Recherche Scientifique (CNRS), European Project, Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Joint Attosecond Science Laboratory, University of Ottawa and National Research Council, University of Ottawa [Ottawa], Institut des Sciences Moléculaires (ISM), Université Montesquieu - Bordeaux 4-Université Sciences et Technologies - Bordeaux 1 (UB)-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Montesquieu - Bordeaux 4-Université Sciences et Technologies - Bordeaux 1-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Université Sciences et Technologies - Bordeaux 1-Université Montesquieu - Bordeaux 4-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Materials science, Atomic Physics (physics.atom-ph), General Physics and Astronomy, FOS: Physical sciences, Physics::Optics, Surface hopping, Grating, 01 natural sciences, Physics - Atomic Physics, Physics - Chemical Physics, 0103 physical sciences, Physical and Theoretical Chemistry, Physics::Chemical Physics, 010306 general physics, Spectroscopy, ComputingMilieux_MISCELLANEOUS, Chemical Physics (physics.chem-ph), 010304 chemical physics, Relaxation (NMR), [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], Rotational temperature, 3. Good health, Excited state, Harmonic, Transient (oscillation), [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, Physics - Optics, Optics (physics.optics)
Abstract

We study theoretically and experimentally the electronic relaxation of NO2 molecules excited by absorption of one ~400 nm pump photon. Semi-classical simulations based on trajectory surface hopping calculations are performed. They predict fast oscillations of the electronic character around the intersection of the ground and first excited diabatic states. An experiment based on high-order harmonic transient grating spectroscopy reveals dynamics occuring on the same timescale. A systematic study of the detected transient is conducted to investigate the possible influence of the pump intensity, pump wavelength, and rotational temperature of the molecules. The quantitative agreement between measured and predicted dynamics shows that, in NO2, high harmonic transient grating spectroscopy encodes vibrational dynamics underlying the electronic relaxation., Comment: The following article has been accepted by Journal of Chemical Physics. After it is published, it will be found at http://jcp.aip.org/

Published
2012
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13. High-order Harmonic Spectroscopy : Experimental and Theoretical study of Cooper Minimum in Argon

Author

Dominique Descamps, Stéphane Petit, Eric Constant, Eric Mével, Bernard Pons, Raluca Cireasa, N Thiré, Baptiste Fabre, Yann Mairesse, Eric Cormier, J. Higuet, H. Ruf, Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
History, Monte Carlo method, chemistry.chemical_element, Electron, Photoionization, 01 natural sciences, 7. Clean energy, Spectral line, 010305 fluids & plasmas, Education, law.invention, law, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Physics::Atomic Physics, 010306 general physics, Spectroscopy, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Argon, Laser, Computer Science Applications, chemistry, Atomic physics, Electron scattering
Abstract

We study the Cooper minimum in HHG from argon atoms using long wavelength laser pulses. We find that the minimum in high harmonic spectra is systematically shifted with respect to total photoionization cross section measurements. We use a semi-classical theoretical approach based on Classical Trajectory Monte Carlo and Quantum Electron Scattering methods (CTMC-QUEST) to model the experiment. Our study reveals that the shift between photoionization and high harmonic emission is due to several effects: the directivity of the recombining electrons and emitted polarization, and the shape of the recolliding electron wavepacket.

Published
2012
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14. Time-resolved predissociation of the vibrationless level of the B state of CH3I

Author

Raluca Cireasa, Valérie Blanchet, Nicolas Thiré, Steven T. Pratt, David Staedter, Femto (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Argonne National Laboratory [Lemont] (ANL), ANR-08-JCJC-0029,HarModyn,Femtochimie par harmoniques d'ordre élevé(2008), European Project, Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
femtochemistry, FOS: Physical sciences, General Physics and Astronomy, 010402 general chemistry, Kinetic energy, 01 natural sciences, Molecular physics, Dissociation (chemistry), symbols.namesake, Ionization, 0103 physical sciences, Physics - Atomic and Molecular Clusters, Physical and Theoretical Chemistry, Physics, 010304 chemical physics, Photodissociation, [PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus], VMI, 0104 chemical sciences, Molecular vibration, Rydberg formula, symbols, Rydberg state, Atomic and Molecular Clusters (physics.atm-clus), Excitation, fs-REMPI
Abstract

The predissociation dynamics of the vibrationless level of the first Rydberg state 6s (B 2E) state of CH3I has been studied by femtosecond-resolved velocity map imaging of both the CH3 and I photofragments. The kinetic energy distributions of the two fragments have been recorded as a function of the pump-probe delay, and as a function of excitation within the umbrella and stretching vibrational modes of the CH3 fragment. These observations are made by using (2+1) Resonant Enhanced MultiPhoton Ionization (REMPI) via the 3pz 2A2" state of CH3 to detect specific vibrational levels of CH3. The vibrational branching fractions of the CH3 are recovered by using the individual vibrationally state-selected CH3 distributions to fit the kinetic energy distribution obtained by using nonresonant multiphoton ionization of either the I or CH3 fragment. The angular distributions and rise times of the two fragments differ significantly. These observations can be rationalized through a consideration of the alignment of the CH3 fragment and the effect of this alignment on its detection efficiency. Two extra dissociation channels are detected: one associated with Rydberg states near 9.2 eV that were observed previously in photoelectron studies, and one associated with photodissociation of the parent cation around 15 eV., Comment: submitted Physical Chemistry Chemical Physics (2011)

Published
2011
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15. High-order harmonic spectroscopy of the Cooper minimum in argon: Experimental and theoretical study

Author

Stéphane Petit, Raluca Cireasa, Nicolas Thiré, Dominique Descamps, Eric Constant, Yann Mairesse, Eric Cormier, Bernard Pons, Baptiste Fabre, H. Ruf, Eric Mével, J. Higuet, Centre d'Etudes Lasers Intenses et Applications (CELIA), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Femto (LCAR), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Conseil Régional d'Aquitaine (20091304003 ATTOMOL and COLA projet), ANR-08-JCJC-0029,HarModyn,Femtochimie par harmoniques d'ordre élevé(2008), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Atomic Physics (physics.atom-ph), Wave packet, FOS: Physical sciences, Photoionization, Electron, 42.65.Ky, 42.65.Re, 32.80.Rm, 7. Clean energy, 01 natural sciences, Physics - Atomic Physics, 010305 fluids & plasmas, ATOMS, CHARGE-TRANSFER, Atomic orbital, PHOTOIONIZATION, Ionization, 0103 physical sciences, Physics::Atomic and Molecular Clusters, High harmonic generation, Physics::Atomic Physics, 010306 general physics, ComputingMilieux_MISCELLANEOUS, ORBITALS, Physics, [PHYS]Physics [physics], [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], Scattering, THRESHOLD-IONIZATION, HYDROGEN, Atomic and Molecular Physics, and Optics, 3. Good health, ALIGNED MOLECULES, LASER, Atomic physics, Electron scattering, Physics - Optics, Optics (physics.optics), GENERATION
Abstract

We study the Cooper minimum in high harmonic generation from argon atoms using long wavelength laser pulses. We find that the minimum in high harmonic spectra is systematically shifted with respect to total photoionization cross section measurements. We use a semi-classical theoretical approach based on Classical Trajectory Monte Carlo and Quantum Electron Scattering methods (CTMC-QUEST) to model the experiment. Our study reveals that the shift between photoionization and high harmonic emission is due to several effects: the directivity of the recombining electrons and emitted polarization, and the shape of the recolliding electron wavepacket., Comment: 13 pages

Published
2011
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16. Molecular photofragment orientation in the photodissociation of H2O2 at 193 nm and 248 nm

Author

Raluca Cireasa, S. A. Seamons, Mark Brouard, T. Perkins, and Yuan-Pin Chang

Subjects
Angular momentum, Zeeman effect, business.industry, Chemistry, Photodissociation, General Physics and Astronomy, Polarization (waves), Molecular physics, symbols.namesake, Optics, Excited state, symbols, Physics::Chemical Physics, Physical and Theoretical Chemistry, Spectroscopy, Laser-induced fluorescence, business, Circular polarization
Abstract

Angular momentum orientation has been observed in the OH(X(2)Π, v = 0) fragments generated by circularly polarized photodissociation of H(2)O(2) at 193 nm and 248 nm. The magnitude and sign of the orientation are strongly dependent on the OH(X) photofragment rotational state. In addition to conventional laser induced fluorescence methods, Zeeman quantum beat spectroscopy has also been used as a complementary tool to probe the angular momentum orientation parameters. The measured orientation at 193 nm is attributed solely to photodissociation via the Ã(1)A state, even though at this wavelength H(2)O(2) is excited near equally to both the Ã(1)A and B(1)B electronic states. This observation is confirmed by measurements of the photofragment orientation at 248 nm, where access to the Ã(1)A state dominates. Several possible mechanisms are discussed to explain the observed photofragment orientation, and a simple physical model is developed, which includes the effects of the polarization of the parent molecular rotation upon absorption of circularly polarized light. Good agreement between the experimental and simulation results is obtained, lending support to the validity of the model. It is proposed that photofragment orientation arises mainly from the coupling of the parent rotational angular momentum with that induced during photofragmentation.

Published
2011

17. Time-resolved photoelectron spectroscopy of the CH3I B1E 6s [2] state

Author

Raluca Cireasa, Steven T. Pratt, Valérie Blanchet, Nicolas Thiré, Femto (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Argonne National Laboratory [Lemont] (ANL), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
010304 chemical physics, Chemistry, Photoemission spectroscopy, General Physics and Astronomy, Photoionization, 010402 general chemistry, 01 natural sciences, Electron spectroscopy, 0104 chemical sciences, X-ray photoelectron spectroscopy, Excited state, Ionization, 0103 physical sciences, Physics::Atomic and Molecular Clusters, Physics::Atomic Physics, Physical and Theoretical Chemistry, Atomic physics, Rydberg state, Time-resolved spectroscopy
Abstract

International audience; The predissociation dynamics of the vibrationless level of the 6s (B 2E) Rydberg state of CH3I was studied by femtosecond-resolved velocity map imaging of photoelectrons. By monitoring the decay of the CH3I+ produced by photoionizing the B state, the predissociation lifetime was measured to be 1310 ± 70 fs. Photoelectron spectra were recorded as a function of the excitation scheme (one or two photons to the B state), and as a function of the ionizing wavelength. All of these photoelectron spectra show a simple time dependence that is consistent with the decay time of the CH3I+ ion signal. The photoelectron angular distributions for the ionization of the B state depend on the excitation scheme and the ionizing wavelength, and show a strong dependence on the vibrational modes excited in the resulting CH3I+. At long delays, the photoelectron spectra are characterized by photoionization of the I(2P1/2) fragment formed by predissociation of the B state.

Published
2010
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18. Quantum Interference in NO2

Author

Valérie Blanchet, Raluca Cireasa, Benjamin J. Whitaker, Jean-Benoît Hamard, Béatrice Chatel, Femto (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, School of Chemistry [Leeds], University of Leeds, ALLIANCE, PPF nanograin, ALLIANCE, European Project: 37686,MOLCOTUV, Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Photon, 010304 chemical physics, Ultraviolet Rays, Chemistry, Nitrogen Dioxide, femtochemistry, Beat (acoustics), 02 engineering and technology, 021001 nanoscience & nanotechnology, NO2, 01 natural sciences, Ion, Oxygen, Wavelength, velocity map imaging, Ionization, 0103 physical sciences, Ultraviolet light, Quantum Theory, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Physical and Theoretical Chemistry, Atomic physics, 0210 nano-technology, Femtochemistry, Quantum
Abstract

This paper investigates the origin of a quantum interference observed when NO(2) is dissociatively ionized by short pulses of ultraviolet light. We describe time-resolved measurements of NO(+), O(+), and NO(2)(+) ions produced following the interaction of NO(2) with a approximately 70 fs duration pulse centered close to 400 nm and a subsequent time-delayed probe pulse close to 269, 205, or 400 nm. A quantum beat oscillation with a period of 524 fs and a characteristic damping time of 8 ps is observed on all transient ion signals. We investigate the effect of tuning the central wavelength of the excitation pulse over a 12 nm range, and we discuss the potential importance of three possible multiphoton pathways involving one, two, and three pump photons. We conclude that the ionization pathway responsible for the beat signal is most likely due to a process involving the absorption of two pump photons and two probe photons. This presents an interesting problem with respect to the interpretation of the mechanism responsible for the quantum interference signature since the electronic states of NO(2) reached at the two-photon level are all thought to be extremely short-lived and to dissociate on a time scale that is far shorter than the characteristic damping time of the oscillatory signals. We suggest that a possible explanation for the observed dynamics is associated with a minor dissociation channel of the (2)(2)B(2) state of NO(2) through its interaction with the longer lived (2)(2)A(1) state.

Published
2010
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19. Collisional depolarization of OH(A) with Ar: Experiment and theory

Author

Sarantos Marinakis, Mark Brouard, F. J. Aoiz, A. M. Green, Yuan-Pin Chang, C. J. Eyles, Raluca Cireasa, A. Bryant, and Jacek Kłos

Subjects
Elastic scattering, Zeeman effect, Chemistry, Inelastic collision, General Physics and Astronomy, Beat (acoustics), Depolarization, Rotational energy, Elastic collision, symbols.namesake, Amplitude, symbols, Physical and Theoretical Chemistry, Atomic physics
Abstract

Zeeman quantum beat spectroscopy has been used to measure the 300 K rate constants for the angular momentum depolarization of OH(A (2)Sigma(+)) in the presence of Ar. We show that the beat amplitude at short times, in the absence of collisions, is well described by previously developed line strength theory for (1+1) laser induced fluorescence. The subsequent pressure dependent decay of the beat amplitude is used to extract depolarization rate constants and estimates of collisional depolarization cross sections. Depolarization accompanies both inelastic collisions, giving rise to rotational energy transfer, and elastic collisions, which change m(j) but conserve j. Previous experimental studies, as well as classical theory, suggest that elastic scattering contributes around 20% to the observed total depolarization rate at low j. Simulation of the experimental beat amplitudes, using theoretical calculations presented in the preceding paper, reveals that depolarization of OH(A) by Ar has a rate constant comparable to, if not larger than, that for energy transfer. This is consistent with a significant tilting or realignment of j(') away from j on collision. The experimental data are used to provide a detailed test of quantum mechanical and quasiclassical trajectory scattering calculations performed on a recently developed ab initio potential energy surface of Kłos et al. [J. Chem. Phys. 129, 054301 (2008)]. The calculations and simulations account well for the observed cross sections at high N, but underestimate the experimental results by between 10% and 20% at low N, possibly due to remaining inaccuracies in the potential energy surface or perhaps to limitations in the dynamical approximations made, particularly the freezing of the OH(A) bond.

Published
2009

20. Spectroscopie d'émission par transformation de fourier des radicaux SiC et HCSi

Author

Raluca, Cireasa, Laboratoire de Photophysique Moléculaire (PPM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Université Paris Sud - Paris XI, Prof. I. Iova et Dr. M. Vervloet, and Cireasa, Dana Raluca

Subjects
[PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], décharge électrique, radicaux libres siliciés, spectroscopie d'émission, spectroscopie par transformation de Fourier, [PHYS.PHYS.PHYS-ATOM-PH] Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph]
Abstract

Le but de cette thèse était d'étudier des radicaux siliciés d'intérêt pour la production de matériaux et couches minces ainsi que d'intérêt astrophysique, notament le radical SiC, en utilisant la technique de spectroscopie d'émission parTransformée de Fourier.Etant connue la difficulté d'obtenir un signal spectroscopique du radical SiC, il a fallu dans un premier temps trouver une source à la fois capable de le produire et appropriée à notre technique d'enregistrement. Les résultats présentés dans ce mémoire montrent qu'en utilisant une décharge électrique continue établie dans untube à décharge de type Schuller dans un mélange d'hélium et d'hexamethyl disilane, il a été possible de produire de manière efficace et reproductible le radical SiC, ainsi qu'un nouveau radical HCSi.En ce qui concerne le radical SiC, nous avons mis l'accent sur l'interprétation du spectre de la transition C3Π-X3Π. L'examen de certaines constantes moléculaires effectives de l'état C3Π indique un comportement anormal de celles-ci avec le nombre quantique de vibration. Pour l'expliquer, nous avons proposé deux hypothèses : une dépendance des constantes d'interaction de spin avec la distance internucléaire et lamanifestation de perturbations de type spin-orbite entre l'état C3Π et d'autres états électroniques proches en énergie.Outre les deux transitions électroniques du radical SiC, grâce à cette source d'émission, nous avons détecté pour la première fois en phase gazeuse le radical silicié HCSi. Les ensembles de constantes moléculaires déterminées pour les niveaux vibroniques observés sont en bon accord avec les calculs ab initio. L'analysespectroscopique et les valeurs anormales de certaines constantes moléculaires indiquent l'existence de perturbations rotationnelles dans le niveau vibrationnel (100) de l'état excité et respectivement, d'une perturbation vibrationnelle dans le niveau vibrationnel (100) de l'état électronique fondamental, due à l'interaction de Fermi avec le niveau (020) du même état.

Published
1999

21. Deposition of carbon nitride thin films by IR-laser-induced reactions in carbon-nitrogen gas-phase compounds

Author

Rodica Alexandrescu, Silviu Cojocaru, A. Andrei, Ion Morjan, Raluca Cireasa, Ashock Kumar, and Aurelian Crunteanu

Subjects
chemistry.chemical_compound, Chemical state, Materials science, Carbon film, X-ray photoelectron spectroscopy, chemistry, Photoemission spectroscopy, Analytical chemistry, chemistry.chemical_element, Chemical vapor deposition, Thin film, Carbon, Carbon nitride
Abstract

Since the theoretical studies of Liu and Cohen who predicted the existence of a superhard phase of carbon nitride, a great deal of effort was underdone in order to synthesize this hypothetical material with a nitrogen content as high as the 57% present in a (beta) -C3N4 structure. This study presents an attempt to produce CNx thin films using the laser-induced CVD technique. CW CO2 laser was used for irradiating various carbon-nitrogen containing mixtures such as C2H4/N2O/NH3. The CNx films were grown alternatively on bare alumina ((alpha) - Al2O3) substrates and on pre-deposited Ti films. A comparative analysis of nitrogen incorporation in the films obtained in different experimental conditions was performed by means of the X-ray photoelectron spectroscopy. The same method was used to identify the chemical states of the CN system.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Published
1998
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22. Laser pyrolysis of carbon-nitrogen gas-phase compounds: An attempted approach to carbon nitride formation

Author

Aurelian Crunteanu, Silviu Cojocaru, I. Morjan, Ion N. Voicu, S. Petcu, D. Fatu, Raluca Cireasa, Friedrich Huisken, Rodica Alexandrescu, Laboratoire de physique des interfaces et des couches minces [Palaiseau] (LPICM), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche en Communications Optiques et Microondes (IRCOM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), and Cojocaru, Costel Sorin

Subjects
010302 applied physics, Inorganic chemistry, Analytical chemistry, Infrared spectroscopy, Carbon composites, 02 engineering and technology, General Chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Decomposition, [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], chemistry.chemical_compound, Crystallinity, Ammonia, chemistry, Acetylene, 0103 physical sciences, X-ray crystallography, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], spectrophotometry, General Materials Science, 0210 nano-technology, Carbon nitride, Pyrolysis, ComputingMilieux_MISCELLANEOUS
Abstract

We describe the possibility to synthesize carbon nitride fine powder by laser pyrolysis of acetylene/nitrous oxide/ammonia mixtures. The powders were produced in a flow reactor by varying the relative concentrations of the sensitizers ( SF 6 C 2 H 4 ). The kinetics of the reaction was monitored by IR spectrophotometry of the exhaust gases. The powder crystallinity and bond structure was studied by X-ray diffraction (XRD) and IR transmission spectrometry, respectively. The majority of XRD data suggests the presence of the predicted α- and β-C3N4 structures, with a concentration depending on starting conditions. The presence of CN bonded phases seems relevant. Under the present conditions, the slight contamination of powders by SF6 decomposition products could not be avoided.

Published
1998

23. Preparation of carbon nitride fine powder by laser induced gas-phase reactions

Author

Friedrich Huisken, Aurelian Crunteanu, Silviu Cojocaru, G. Pugna, I. Morjan, S. Petcu, Rodica Alexandrescu, Raluca Cireasa, Laboratoire Francis PERRIN (LFP - URA 2453), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche en Communications Optiques et Microondes (IRCOM), Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM), Laboratoire de physique des interfaces et des couches minces [Palaiseau] (LPICM), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Analytical chemistry, chemistry.chemical_element, 02 engineering and technology, General Chemistry, Nitride, 021001 nanoscience & nanotechnology, Laser, 01 natural sciences, Nitrogen, law.invention, Ammonia, chemistry.chemical_compound, chemistry, Chemical engineering, X-ray photoelectron spectroscopy, law, 0103 physical sciences, X-ray crystallography, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, 0210 nano-technology, Pyrolysis, Carbon nitride
Abstract

International audience; We present the possibility of carbon nitride fine powder synthesis by sensitized laser pyrolysis of acethylene/nitrous oxide/ammonia mixtures. The powders were analyzed using X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and IR transmission measurements. It was found that nitrogen was incorporated in powders and that in the carbon-nitrogen phases formed, the presence of the triple bonded C≡N was not detected. The majority of X-ray diffraction data suggests the presence of a mixture of the predicted α- and β-C3N4 structure, with an α-C3N4-like form being prevalent. The powders were found to be slightly contaminated by SF6 sensitizer products. Our results suggest that by improving the experimental parameters this contamination might be reduced and that the laser pyrolysis method offers possibilities for production of CxNy materials, with controlled composition.

Published
1997
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24. Imaging fast relaxation dynamics of NO2

Author

Valérie Blanchet, Raluca Cireasa, Cécile Maury, Jean-Benoît Hamard, Femto (LCAR), Laboratoire Collisions Agrégats Réactivité (LCAR), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Intra-European Marie Curie fellowship- contract MOLCOTUV-041732 Plan Etat-Région: Spectroscopies Optiques Ultimes, ANR-06-BLAN-0004,cocomouv,Shaped tunable ultraviolet femtosecond source: Application to coherent control in atoms and molecules.(2006), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées

Subjects
Physics, Photon, 010304 chemical physics, femtochemistry, Photoelectric effect, NO2, 010402 general chemistry, Condensed Matter Physics, Kinetic energy, 01 natural sciences, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, symbols.namesake, Velocity map imaging, 0103 physical sciences, Rydberg formula, symbols, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, Rydberg state, Spectroscopy, 33.80.Gj, 42.65.Re, 33.60.+q, 33.80.Rv, 37.20+j, 33.80.Eh, Femtochemistry, Mathematical Physics, Excitation
Abstract

Time-resolved spectroscopy combined with velocity map imaging techniques have been used to investigate the multiphoton dynamics of the NO2 molecule. Two different pump–probe excitation schemes were used to explore different potential energy surfaces (PESs) located in the first dissociation region and in the Rydberg region around 9.2 eV. Integrated and energy-resolved signals of NO2 +, NO+ and photoelectrons were recorded as a function of time. When exciting with 403 nm photons, the NO+ signal exhibits an intriguing oscillatory behaviour with a period of 512 fs. The NO+ and photoelectron kinetic energy distributions produced by this pump wavelength were cold, while those produced when employing 269 nm photons as pump were very rich, evidencing the presence of multiple excitation channels. A couple of sharp long-lived photoion–photoelectron peaks represents the most salient feature of the latter. They were assigned to an excitation by two 269 nm photons to a Rydberg state dissociating into NO(A2Σ+)+O(3P). This NO+ peak as well as another one located at 0 eV display very complex time dependencies including the signatures of two dissociation dynamics on timescales of 400 and 600 fs. The different pathways responsible for this temporal behaviour are discussed in view of shedding light onto the underlying multichannel multiphoton dynamics.

Published
2009
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25. Infrared and ultraviolet laser‐assisted deposition from iron pentacarbonyl

Author

Ion N. Voicu, Raluca Cireasa, Dan C. Dumitras, Ion Morjan, and Rodica Alexandrescu

Subjects
Materials science, Infrared, General Engineering, Analytical chemistry, medicine.disease_cause, Laser, Atomic and Molecular Physics, and Optics, Iron pentacarbonyl, law.invention, chemistry.chemical_compound, chemistry, law, medicine, Deposition (phase transition), Irradiation, Absorption (electromagnetic radiation), Quartz, Ultraviolet
Abstract

Laser-induced Fe(CO)5 decomposition at different vapor pressures was performed, and a comparative study of the films obtained thermally (at 10.6 ?m) and photolytically (at 248 nm) is presented. A perpendicular geometry of irradiation and quartz substrates were used. The influence of the incident laser energy on the growth rate and on the chemical content of the films was demonstrated. The film properties are discussed in connection with the irradiation conditions and specific mechanisms involved.

Published
1996
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26. Carbon nitride thin films and nanopowders produced by CO2 laser pyrolysis

Author

F. Vasiliu, I. Morjan, Aurelian Crunteanu, Ashok Kumar, Raluca Cireasa, Costel Sorin Cojocaru, and Rodica Alexandrescu

Subjects
010302 applied physics, Materials science, Silicon, Nucleation, Mineralogy, chemistry.chemical_element, 02 engineering and technology, Surfaces and Interfaces, Substrate (electronics), 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Surfaces, Coatings and Films, chemistry.chemical_compound, Chemical engineering, X-ray photoelectron spectroscopy, chemistry, 0103 physical sciences, Materials Chemistry, Crystallite, Thin film, 0210 nano-technology, Carbon nitride, Pyrolysis
Abstract

Nanocrystalline CNx particles and thin films were produced in a flow reactor system by the CO2 laser pyrolysis of sensitised NH3–N2O–C2 H2reactant gas mixtures. Depending on the substrate nature (silicon or quartz) the SEM and TED analysis of the CNx thin films revealed specific nucleation and growth morphologies of crystallites, resembling the β-C3 N4 phase. In the case of C3 N4 nanopowder synthesis, the relative concentration of the sensitisers (SF6 /C2 H4 ) was varied to minimise SF6 decomposition. The majority of the data obtained from powder analysis (XRD, XPS, and ir transmission measurements) suggests the presence of CN bonded phases and the formation of α-and β-C3 N4 structures.

27. Influence of process parameters on CNx films obtained by laser-CVD at two wavelengths

Author

I. Morjan, Raluca Cireasa, Aurelian Crunteanu, Ion N. Mihailescu, G. Oncioiu, C. Martin, and Rodica Alexandrescu

Subjects
Infrared, Analytical chemistry, chemistry.chemical_element, General Chemistry, Chemical vapor deposition, medicine.disease_cause, Laser, Nitrogen, law.invention, chemistry.chemical_compound, chemistry, X-ray photoelectron spectroscopy, law, medicine, General Materials Science, Carbon nitride, Chemical composition, Ultraviolet
Abstract

The carbon nitride (CN x ) films have been prepared by infrared (IR; at 10.6 μm) and ultraviolet (at 248 nm) laser induced chemical vapour deposition (CVD) using different ethylene/nitrous oxide/ammonia mixtures. The partial concentration of ammonia in mixtures was varied in order to obtain a higher nitrogen incorporation in the deposited films. The changes induced in the gas-phase composition by the laser radiation in different experimental conditions were determined by IR transmission measurements. The film composition was studied by X-ray photoelectron spectroscopy. The modification of the film chemical composition, specifically the dependence of the N C ratio, on the irradiation wavelength and on the reactants composition is described for the first time.

28. Synthesis of crystalline structures of CNx thin films deposited on sapphire, quartz and alumina substrates

Author

Rodica Alexandrescu, I. Morjan, Raluca Cireasa, Costel Sorin Cojocaru, Ashock Kumar, Aurelian Crunteanu, and F. Vasiliu

Subjects
Ethylene, Materials science, chemistry.chemical_element, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, chemistry.chemical_compound, Ammonia, X-ray photoelectron spectroscopy, chemistry, Chemical engineering, 0103 physical sciences, Sapphire, Thin film, 010306 general physics, 0210 nano-technology, Carbon nitride, Carbon, Quartz
Abstract

Carbon nitride films raise current interest for their potential applications as ultrahard materials. We report on the formation of crystalline CN structures in films deposited at 248 nm on different substrates (sapphire, quartz, alumina) using the laser-induced CVD method and a gas mixture containing ethylene/nitrous oxide and ammonia as carbon and nitrogen source, respectively. The structural and morphological properties of the films were characterized by different analytical techniques (SEM, TEM, TED and XPS).

29. Carbon nitride thin films synthesized from the gas-phase by laser-induced reactions: A parametric study

Author

Alexandrescu, R., Crunteanu, A., Raluca Cireasa, Cojocaru, S., Morjan, I., Kumar, A., Cojocaru, Costel Sorin, Y-W. Chung, R.W.J. Chia, and A. Kumar, Institut de Recherche en Communications Optiques et Microondes (IRCOM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique des interfaces et des couches minces [Palaiseau] (LPICM), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Y-W. Chung, R.W.J. Chia, and and A. Kumar

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], ComputingMilieux_MISCELLANEOUS, [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci]
Abstract

International audience

30. Inhomogeneous high harmonic generation in krypton clusters

Author

Nicolas Thiré, Raluca Cireasa, Eric Mével, Stéphane Petit, Yann Mairesse, C. Handschin, Dominique Descamps, Eric Constant, H. Ruf, Valérie Blanchet, and Baptiste Fabre

Subjects
chemistry.chemical_compound, Light intensity, Monomer, chemistry, Krypton, Cluster (physics), High harmonic generation, chemistry.chemical_element, Atomic physics, Radiation, Ultraviolet radiation, Coherence (physics)
Abstract

By performing high harmonic generation in a cluster and monomer mixture, we isolate the radiation originating from clusters. Surprisingly this radiation is depolarized. Our experiments show that it is produced by a new recollisional mechanism.

31. Deposition of metallic thin layers by photolytic versus thermal-laser-induced processes

Author

Rodica Alexandrescu, Ioan Ursu, Letitia Voicu, Ion Morjan, Raluca Cireasa, and A. Andrei

Subjects
Atomic layer deposition, Materials science, Chemical engineering, law, Physical vapor deposition, Inorganic chemistry, Deposition (phase transition), Chemical vapor deposition, Thin film, Laser, Layer (electronics), law.invention, Pulsed laser deposition
Abstract

Laser-assisted processes for metal-based thin films deposition are currently using vapour-phase precursors. Eitherphotolytic or thermal, the mechanisms developed during laser-induced interaction between adsorbed precursor and substrate are imposing different trends to the composition and morphology of the growing metallic layer. Various aspects of the dynamics of film growth are discussed, in connection with the deposition oftitanium from titanium tetrachioride.Keywords: laser induced photochemistry, laser CVD, laser pyrolysis, laser photolysis. I . INTRODUCTION In the frame of the applications of lasers as tools for fine processing of surfaces, local deposition of films from vapour-phase is one of the most important and successfully developing field of tiga' Depending on the radiation action on the gas or absorbate precursor, laser methods are often roughly devided in photolytic or thermal-activatedprocesses. Metal containing precursors, either organometallics (carbonyls, alkyls) or inorganic salts (titanium chloride)

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