Peer-reviewed Publications |
Azima, A., Duesterer, S., Radcliffe, P., Redlin, H., Stojanovic, N., Li, W., Schlarb, H., Feldhaus, J., Cubaynes, D., Meyer, M., Dardis, J., Hayden, P., Hough, P., Richardson, V., Kennedy, E. T., & Costello, J. T. (2009). Time-resolved pump-probe experiments beyond the jitter limitations at FLASH. APPLIED PHYSICS LETTERS, 94(14).
Résumé: Using a noninvasive, electro-optically based electron bunch arrival time measurement at FLASH (free electron laser in Hamburg) the temporal resolution of two-color pump-probe experiments has been significantly improved. The system determines the relative arrival time of the extended ultraviolet pulse of FLASH and an amplified Ti:sapphire femtosecond-laser pulse at the interaction region better than 90 fs rms. In a benchmarking pump-probe experiment using two-color above threshold ionization of noble gases, an enhancement in the timing resolution by a factor of 4 compared to the uncorrected data is obtained.
|
|
Bizau, J. - M., Mosnier, J. - P., Kennedy, E. T., Cubaynes, D., Wuilleumier, F. J., Blancard, C., Champeaux, J. - P., & Folkmann, F. (2009). Photoionization of the Ne-like Si4+ ion in ground and metastable states in the 110-184-eV photon energy range. PHYSICAL REVIEW A, 79(3).
Résumé: We present measurements of the absolute photoionization cross section of the neonlike Si4+ ion over the 110-184 eV photon energy range. The measurements were performed using two independent merged-beam setups at the super-ACO and ASTRID synchrotron-radiation facilities, respectively. Signals produced in the photoionization of the 2p subshell of the Si4+ ion both from the 2p(6) S-1(0) ground state and the 2p(5)3s P-3(0,2) metastable levels were observed. Calculations of the 2p photoionization cross sections were carried out using a multi-configuration Dirac-Fock code. They give results in good agreement with the measured spectra. Comparison with other available theoretical results is also presented.
|
|
Cubaynes, D., Guilbaud, S., Wuilleumier, F. J., Meyer, M., Heinecke, E., Riek, K., Zimmermann, P., Yalcinkaya, M., Fritzsche, S., Strakhova, S. I., & Grum-Grzhimailo, A. N. (2009). Photoionization from the 2p subshell of the laser-excited aligned Na*2p(6)3p P-2(3/2) state. PHYSICAL REVIEW A, 80(2).
Résumé: High resolution angle-resolved photoelectron spectra from Na atoms laser excited and aligned in the Na* 2p(6)3p P-2(3/2) state are investigated experimentally and theoretically in the region of the Na+ 2p(5)3p manifold. A prominent influence of the alignment on the relative line intensities is observed. The measured linear alignment dichroism is in good agreement with the theoretical results obtained in the multiconfigurational Dirac-Fock approximation as well as in a generalized geometrical model, which is extended to the description of angular distributions of photoelectrons from polarized atoms.
|
|
Dowek, D., Haouas, A., Guillemin, R., Elkharrat, C., Houver, J. - C., Li, W. B., Catoire, F., Journel, L., Simon, M., & Lucchese, R. R. (2009). Recoil frame photoemission in inner-shell photoionization of small polyatomic molecules. EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, 169, 85–93.
Résumé: Going from a diatomic to a polyatomic linear or non-linear molecule, the description of molecular frame photoemission in photoionization of molecules involves a function of increasing complexity. Using the electron-ion Vector Correlation method, which provides the emission velocity vectors of the emitted charged particles in a dissociative photoionization reaction, generally gives access to Recoil Frame Photoelectron Angular Distributions (RFPADs). We report results for site selected inner-shell photoionization of the N(2)O molecule induced by elliptically polarized light, where the primary ionization reaction leads to the production of several fragmentation channels. Ion fragment kinetic energy release distributions as well as RFPADs are reported for selected two ion-channels containing the complete parent molecule. Experimental results are compared with recent multi-channel Schwinger configuration interaction (MCSCI) ab initio calculations at the level of the RFPADs. The link with the original computed molecular frame photoelectron angular distributions (MFPADs) is discussed.
|
|
Dowek, D., Picard, Y. J., Billaud, P., Elkharrat, C., & Houver, J. C. (2009). Molecular Frame Photoemission: Probe of the Photoionization Dynamics for Molecules in the Gas Phase. CHINESE JOURNAL OF CHEMICAL PHYSICS, 22(2), 178–186.
Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. This paper reports a comparative study of non-resonant and resonant photoionization of D(2) induced by VUV circularly polarized synchrotron radiation at SOLEIL at the level of the molecular frame photoelectron angular distributions (MFPADs). We use the vector correlation method which combines imaging and time-of-flight resolved electron-ion coincidence techniques, and a generalized formalism for the expression of the I(chi, theta(e), phi(e)) MFPADs, where chi is the orientation of the molecular axis with respect to the light quantization axis and (theta(e), phi(e)) the electron emission direction in the molecular frame. Selected MFPADs for a molecule aligned parallel or perpendicular to linearly polarized light, or perpendicular to the propagation axis of circularly polarized light, are presented for dissociative photoionization (DPI) of D(2) at two photon excitation energies, hv=19 eV, where direct PI is the only channel opened, and hv=32.5 eV, i.e. in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. We discuss in particular the properties of the circular dichroism characterizing photoemission in the molecular frame for direct and resonant PI. In the latter case, a remarkable behavior is observed which may be attributed to the interference occurring between undistinguishable autoionization decay channels.
|
|
El Hassan, N., Bizau, J. M., Blancard, C., Cosse, P., Cubaynes, D., Faussurier, G., & Folkmann, F. (2009). Photoionization cross sections of iron isonuclear sequence ions: Fe2+ to Fe6+. PHYSICAL REVIEW A, 79(3).
Résumé: We have measured the absolute photoionization cross sections of Fe2+ to Fe6+ ions in the photon energy range covering the first ionization threshold up to 160 eV. Particular interest is emphasized on the region of the 3p -> 3d excitations. The experimental data are compared to the results of calculations we have performed using a spectral opacity code, as well as to available R-matrix and one-electron calculations. It is shown that often the theoretical results tend to overestimate the intensity of the 3p -> 3d photoexcitations. An anomalously low value of the integrated oscillator strength is measured for Fe2+ ion.
|
|
Feagin, J. M., Colgan, J., Huetz, A., & Reddish, T. J. (2009). Electron-Pair Excitations and the Molecular Coulomb Continuum. PHYSICAL REVIEW LETTERS, 103(3), 033002.
Résumé: Electron-pair excitations in the molecular hydrogen continuum are described by quantizing rotations of the momentum plane of the electron pair about the pair's relative momentum. A heliumlike description of the molecular photodouble ionization is thus extended to higher angular momenta of the electron pair. A simple three-state superposition is found to account surprisingly well for recent observations of noncoplanar electron-pair, molecular-axis angular distributions.
|
|
|
Gaaloul, N., Jaouadi, A., Pruvost, L., Telmini, M., & Charron, E. (2009). Controlled deflection of cold atomic clouds and of Bose-Einstein condensates. EUROPEAN PHYSICAL JOURNAL D, 53, 343.
|
|
Grum-Grzhimailo, A. N., Gryzlova, E. V., Cubaynes, D., Heinecke, E., Yalcinkaya, M., Zimmermann, P., & Meyer, M. (2009). The generalized geometrical model for the photoionization of polarized atoms: application to linear dichroism in the 2p photoemission from Na 3(2)S and Na*3(2)P initial states. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(17).
Résumé: The generalized geometrical model utilized for the interpretation of photoelectron spectra is extended to the photoionization from polarized atoms. Within this model, the linear magnetic and the linear alignment dichroisms in the photoemission are calculated. The theoretical results are compared to those obtained from high-resolution angle-resolved photoelectron spectra, which were recorded upon 2p(-1) photoionization of sodium atoms oriented in the Na 2p(6)3s S-2(1/2) ground and Na* 2p(6)3p P-2(1/2) laser-excited states or aligned in the Na* 2p(6)3p P-2(3/2) state. Good overall agreement is found between theory and experiment.
|
|
|
Kelkensberg, F., Lefebvre, C., Siu, W., Ghafur, O., Nguyen-Dang, T. T., Atabek, O., Keller, A., Serov, V., Johnsson, P., Swoboda, M., Remetter, T., L’Huillier, A., Zherebtsov, S., Sansone, G., Benedetti, E., Ferrari, F., Nisoli, M., Lépine, F., Kling, M. F., & Vrakking, M. J. J. (2009). Molecular Dissociative Ionization and Wave-Packet Dynamics Studied Using Two-Color XUV and IR Pump-Probe Spectroscopy. PHYSICAL REVIEW LETTERS, 103, 123005.
|
|
Kheifets, A. S., Naja, A., Casagrande, E. M. S., & Lahmam-Bennani, A. (2009). An energetic (e, 2e) reaction away from the Bethe ridge: recoil versus binary. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(16).
Résumé: We analyse the recoil-to-binary (RB) peak intensity ratio in an energetic (e, 2e) reaction performed on the valence ns sub-shell of noble gas atoms away from the Bethe ridge condition. A qualitative change in the RB ratio dependence on the ejected electron energy from He to Ar can be explained by the variation of reflectivity of the short-range Hartree-Fock potential. The reflectivity increases profoundly from lighter (He) to heavier (Ne and Ar) noble gas atoms because of modification of the scattering phases due to occupation of the target p orbitals (Levinson-Seaton theorem). This effect is further modified due to strong inter-shell correlations in Ar. These theoretical predictions are confirmed experimentally.
|
|
Lahmam-Bennani, A., Casagrande, E. M. S., & Naja, A. (2009). Experimental investigation of the triple differential cross section for electron impact ionization of N-2 and CO2 molecules at intermediate impact energy and large ion recoil momentum. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(23).
Résumé: The (e, 2e) triple differential cross sections (TDCS) are measured for the ionization of nitrogen and carbon dioxide molecules in a coplanar asymmetric geometry for a wide range of ejected electron energies and at an incident energy about 500-700 eV. This kinematics corresponds to a large momentum imparted to the ion, and is meant to enhance the recoil scattering. The experimental binary and recoil angular distributions of the TDCS are characterized both by a shift towards larger angles with respect to the momentum transfer direction and by a large intensity in the recoil region, in particular for the ionization of the 'inner' N-2(2 sigma(g)) molecular orbital. The data are compared with the results of calculations using the first Born approximation-two centre continuum (FBA-TCC) theoretical model for treating differential electron impact ionization. The experimentally observed shifts and recoil intensity enhancement are not predicted by the model calculations, which rather yield a TDCS symmetrically distributed around the momentum transfer direction, and completely fail in describing the recoil distribution. It is hoped that these new results will stimulate the development of more refined theories for correctly modelling single ionization of molecules.
|
|
Lahmam-Bennani, A., Naja, A., Casagrande, E. M. S., Okumus, N., Dal Cappello, C., Charpentier, I., & Houamer, S. (2009). Dynamics of electron impact ionization of the outer and inner valence (1t(2) and 2a(1)) molecular orbitals of CH4 at intermediate and large ion recoil momentum. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 42(16).
Résumé: The triply differential cross section has been measured for electron-impact ionization of the outer valence 1t(2) and the inner valence 2a(1) orbitals of methane using the (e,2e) technique with coplanar asymmetric kinematics. The measurements are performed at scattered electron energy of 500 eV, ejected electron energy of 12, 37 and 74 eV and for scattering angle of the fast outgoing electron of 6 degrees. This kinematics is characterized by a target ion recoil momentum ranging from moderate (0.25 au) to very large (3.2 au) values. The results are compared with theoretical cross sections calculated using the 1CW and the BBK models recently extended to molecules. The experimental cross sections exhibit a very large recoil scattering, especially for the inner 2a(1) molecular orbital, which is not predicted by the theory. The differences between experiment and theory are attributed to the very strong scattering from the ion, not properly accounted for by theory. This indicates the need for further theoretical developments as well as experimental investigations in order to correctly model the process of molecular ionization.
|
|
Lebech, M., Houver, J. C., & Dowek, D. (2009). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. I. Ion-electron kinetic energy correlation and laboratory frame photoemission. JOURNAL OF CHEMICAL PHYSICS, 130(19), 194307.
Résumé: The (V(A+), V(e), e) vector correlation method, combining imaging and time-of-flight resolved electron-ion coincidence techniques, is used to probe dissociative photoionization (DPI) of CO induced by vacuum ultra violet linearly or circularly polarized synchrotron radiation in the 26-33 eV photon excitation energy range. It provides original information about both the photoionization dynamics of the CO molecule and the dissociation dynamics of the CO(+) molecular ions. The explored region corresponds to valence and inner-valence CO(+) ionic states, which involve doubly or multiply excited electronic configurations. In this paper I we identify up to 17 DPI reaction pathways by the position of the intermediate CO(+) molecular states in the Franck-Condon region and the (C(+) + O) or (O(+) + C) dissociation limits to which they correlate. For these processes we report the laboratory frame beta(C+/O+) and beta(e) asymmetry parameters as well as the relative branching ratios in selected binding energy bands. The I(chi,theta(e),phi(e)) molecular frame photoelectron angular distributions for selected PI processes will be reported in a companion paper II and compared with multichannel Schwinger configuration interaction ab initio calculations of these observables.
|
|
|
Lefebvre, R., & Atabek, O. (2009). Unusual low-intensity regime in laser-induced molecular photodissociation. International Journal of Quantum Chemistry, 109, 3423.
|
|
|
Lefebvre, R., Atabek, O., Šindelka, M., & Moiseyev, N. (2009). Resonance Coalescence in Molecular Photodissociation. PHYSICAL REVIEW LETTERS, 103(12), 123003.
|
|
|
Milman, P., Keller, A., Charron, E., & Atabek, O. (2009). Molecular orientation entanglement and temporal Bell-type inequalities. EUROPEAN PHYSICAL JOURNAL D, 53, 383.
|
|
Actes de Conférences |
Colgan, J., Reddish, T. J., Huetz, A., Bolognesi, P., Avaldi, L., Gisselbrecht, M., Lavollee, M., & Pindzola, M. S. (2009). The 'KER' effect in the double photoionization of H(2). In INTERNATIONAL CONFERENCE ON MANY PARTICLE SPECTROSCOPY OF ATOMS (Vol. 141).
Résumé: Recent experimental and theoretical work examining the double photoionization of H(2) has uncovered surprising changes in the fully differential cross sections as a function of the kinetic energy released to the protons (which is equivalent to different internuclear separations of the molecule). We describe the recent joint theoretical and experimental investigations which have uncovered the physical reasons for this phenomenon. We show that the observed variations are solely due to the epsilon(Sigma) component of the polarization vector along the molecular axis. Our conclusions are supported by further investigations of the photoionization of H(2)(+), in which similar dramatic variations in the photoelectron angular distributions for the sigma(g) -> sigma(u) transition are found as the internuclear separation is varied. The angular distributions for the sigma(g) -> pi(u) transition show little dependence on the internuclear separation.
|
|
Goddet, J. P., Sebban, S., Guilbaud, O., Gautier, J., Zeitoun, P., Valentin, C., Tissandier, F., Marchenko, T., Lambert, G., Nejdl, J., Cros, B., Maynard, G., Robillard, B., Kazamias, S., Cassou, K., Klisnick, A., Ros, D., Benredjem, J., Mocek, T., Kozlova, M., & Jakubczak, K. (2009). Characterization of a Seeded Optical-Field Ionized Collisional Soft X-Ray Laser. In X-RAY LASERS 2008 (Vol. 130, pp. 135–142). Springer Proceedings in Physics, 130.
Résumé: By seeding ail optical-field-ionized population inverted plasma amplifier with the 25th harmonic of an infrared laser we have produced a compact, diffraction-limited and Fourier-limited laser beam in the soft x-ray spectral range. This laser beam is emitted within a cone of 0.7 mrad at a repetition rate of 10 Hz at a central wavelength of 32.8 nm, The beam exhibits a regular Gaussian spatial profile, and wavefront distortions smaller than lambda/17. The measured coherence time of 5.5 ps is equal to the duration of the lifetime of the amplifying plasma which shows that this source has reached the Fourier limit.
|
|
Guilbaud, O., Goddet, J. P., Sebban, S., Joyeux, D., Ros, D., Gautier, J., Cassou, K., Kazamias, S., Klisnick, A., Habib, J., Zeitoun, P., Benredjem, D., de Rossi, S., Maynard, G., Cros, B., Boudaa, A., Phalippou, D., & Calisti, A. (2009). Temporal Coherence and Spectral Linewidth of a Seeded Soft X-Ray Laser Pulse. In X-RAY LASERS 2008 (Vol. 130, pp. 193–198). Springer Proceedings in Physics, 130.
Résumé: We present in this paper the first measurement of the spectral profile of a seeded soft x-ray laser. Using a varying path difference interferometer the temporal coherence of a seeded OFI x-ray laser has been experimentally determined, leading to a coherence length of 5ps of the order of the gain lifetime. The measured bandwidth is of order 3.4 m angstrom which is in good agreement with the prediction of a theoretical model presented here.
|
|
Habib, J., Klisnick, A., Guilbaud, O., Joyeux, D., Zielbauer, B., Kazamias, S., Ros, D., de Dortan, F., & Pittman, M. (2009). Temporal Coherence and Spectral Line Shape of a GRIP Transient X-Ray Laser. In X-RAY LASERS 2008 (Vol. 130, pp. 115–121).
Résumé: We have used a variable path-difference, wavefront-division interferometer to measure the temporal coherence of an unseeded Ni-like Mo GRIP X-ray laser. This quantity is inversely related to its spectral linewidth. We have investigated the role of several pump parameters on the inferred spectral width. Along this experiment, particular attention has been paid on the source stability.
|
|
Klisnick, A., Larroche, O., De Dortan, F., Habib, J., Guilbaud, O., Kazamias, S., Ros, D., & Zielbauer, B. (2009). Recent Developments on Seeded or Unseeded Transient X-Ray Lasers. In X-RAY LASERS 2008 (Vol. 130, pp. 221–229).
Résumé: The COLAX code was used to investigate the role of several parameters oil the spatial and temporal behaviour of the output pulse of a transient X-ray laser seeded by a harmonic pulse. The importance of the collisional linewidth oil the duration of the output pulse is underlined.
|
|
Margarone, D., Kozlova, M., Nejdl, J., Rus, B., Mocek, T., Homer, P., Polan, J., Stupka, M., Jamelot, G., Cassou, K., Kazamias, S., Klisnick, A., Ros, D., Bercegol, H., Danson, C., & Hawkes, S. (2009). Laser-induced damage studies in optical elements using X-ray laser interferometric microscopy. In DAMAGE TO VUV (Vol. 7361, 73610N). Proceedings of SPIE, 7361.
Résumé: Results of a novel X-ray laser application, aimed at understanding the microscopic effects involved in formation of laser-induced damage in optical materials exposed to sub-ns laser pulses, will be presented. Specifically, we studied thin plane beamsplitters that are presently the weakest element of the next generation of high-energy lasers (LMJ, NIF), with permanent damage threshold below 20 J/cm(2). Standard fused silica substrates and a model system, containing well-defined micron grooves as seeding sites to trigger damage when irradiated by 438 nm laser pulses, were in situ probed by a neon-like zinc X-ray laser delivering up to 10 mJ at 21.2 nm. The probing beamline employed a double Lloyd's mirror interferometer, used in conjunction with an imaging mirror to provide magnification of similar to 8. In conjunction with an array of in-situ optical diagnostics, one of the questions addressed was whether the damage (transient or permanent) on the rear surface of the beamsplitter occurs during or after the laser pulse, i.e. whether it is due to local electrical fields or to other processes. Another issue, examined by both the X-ray interferometric microscopy and the optical diagnostics, is whether a local rear-surface modification is associated with non-linear effects (self-focusing, filamentation) of the laser beam in the bulk.
|
|
Ros, D., Kazamias, S., Guilbaud, O., Habib, J., Zielbauer, B., Pittman, M., Jamelot, G., Klisnick, A., Lagron, J. - C., Joyeux, D., de Rossi, S., Delmotte, F., Lacombe, S., Porcel, E., Lesech, C., Penhoat, A. M., & Touati, A. (2009). Recent Advances on LASERIX Facility: Development of XUV Sources System and Applications. Perspectives from 2008 to 2010. In X-RAY LASERS 2008 (Vol. 130, pp. 13–22).
Résumé: LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam that could also be used to produce synchronized XUV sources. This experimental configuration highly enhances the scientific opportunities of the facility, giving thus the opportunity to realize both X-ray laser experiments and more generally pump/probe experiments, mixing IR and XUV sources. In this contribution, the main results concerning both the development of XUV sources (in the seeded or ASE mode) and their use for applications (irradiation of DNA samples) are presented.
|
|
Rottke, H., Guyetand, O., Gisselbrecht, M., Huetz, A., Agostini, P., Carre, B., Breger, P., Gobert, O., Garzella, D., Hergott, J. - F., Tcherbakoff, O., Merdji, H., Bougeard, M., Boettcher, M., Zhavoronkov, N., Ansari, Z., Sandner, W., Antoine, P., & DiMauro, L. F. (2009). Photoionization in combined ultra short XUV and infrared laser pulses. In INTERNATIONAL CONFERENCE ON MANY PARTICLE SPECTROSCOPY OF ATOMS (Vol. 141).
Résumé: Multi-photon-double ionization of xenon by Ti:Sapphire laser pulses combined with their 25(th) harmonic has been studied by means of a momentum imaging spectrometer. The determination of the momenta of the emitted photoelectron pair and of its energy and angular correlation gives insight into the various mechanisms leading to double ionization. Although the conditions for non sequential direct multi-photon double ionization are met in the experiment, it is found that two-step sequential processes prevail.
|
|
