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A theoretical study of the rotational dynamics of a linear polar molecule in a two-color non-resonant cw laser field is presented. By systematically considering the interactions of this field with the electric dipole moment, polarizability and hyperpolarizability of the molecule, the effect of the symmetries of the Hamiltonian on the orientation and alignment is explored in a regime where the time-average approximation does not hold. It is shown that the alignment and orientation satisfy certain symmetries as a function of the phases and field strengths. On average a one-color cw laser field doest not orient the molecule, being necessary a two-color one having odd and even products of the laser frequency to break the head-versus-tail order confinement., 12 pages, 10 figures

The full permanent magnet "supernanogan" type ECR (electron cyclotron resonance) ion source, SIMPA (Source d'Ions Multicharges de Paris) has been jointly operated by LKB (Laboratoire Kastler Brossel) and INSP (Institut des NanoSciences de Paris) since 2004. Since this time numerous projects have been started to use the extracted beam in atomic physics and surface physics experiments and the x-ray radiation of the ECR plasma for plasma and atomic physics investigations. In this paper recent achievements will be reported that include the first use of an electrostatic ion trap * for trapping highly charged ions on the beam line of an ECR ion source and electron temperature and density measurements with the help of the observation of the bremsstrahlung spectrum of the electrons in the ECR plasma of the source.** Also a new vacuum double crystal spectrometer *** is under construction in our lab that will allow us to measure the very narrow inner shell transitions of highly charged ions produced in the ECR plasma and provide new x-ray standards with this method for the atomic physics community.

International audience; An increasing number of experiments in the field of low energy ion physics (< 25 keV/charge) requires pulsed beams of highly charged ions. Whereas for high-intensity beams (> µA) a pulsed beam chopper, installed downstream to the analyzing dipole, is used. For low-intensity beams (< 100 nA) the ion intensity delivered during the pulse may be increased by operating the ECR discharge in the afterglow mode [1]. This method gives satisfactory results (ie average current during the beam pulse is higher than the current in the CW mode) for high charge state ions. In this paper, we report on results of the afterglow mode for beams of 22Neq+, 36Arq+ and 84Krq+ ions. Furthermore, a new promising “Micro Pulsed Beam” mode will be described with encouraging preliminary results for 84Kr27+ and 36Ar17+ ions.

International audience; We use decelerated (below 20 MeV/u) H-like heavy ions extracted from the GSI-ESR storage ring to study electron capture processes such as Radiative Electron Capture (REC) and Mechanical Electron Capture (MEC) in channeling conditions. With the help of simulations, we show that MEC occurs at relatively large impact parameters into highly excited states. REC studies provide information about the electron gas polarization.

International audience; Interaction of high intensity ultrashort laser pulses with matter has received considerable attention in the last few years. With clusters in intense optical fields (F > 109 V/cm), the energy coupling between radiation and matter is extremely efficient, providing specific features that are not observed when atoms, small molecules or even solid are used as targets : multicharged ions reaching the MeV, hot electrons up to few keV and keV x-ray photons are produced in the laser heated cluster plasma. Here, we focus on the x-ray generation related to the production of highly stripped and excited ions. We study deexcitation of species from Ar12+ to Ar16+ with K vacancy for Ar clusters and from Xe24+ to Xe34+ with L vacancies for Xe clusters. The goal is to understand how electrons initially produced by Optical Field Ionisation (OFI) can reach enough energy to generate a strong production of ions with inner shell vacancies. We have performed quantitative studies(*) on the evolution of absolute photon emission yields and complete charge state distributions with different physical parameters governing the interaction ; namely intensity, polarization, pulse duration and wavelength of the laser, size and atomic number of the clusters. KeV x-rays are studied from rare-gas clusters irradiated with intense (I ~ 1014–1018 W cm-2) infrared and blue laser pulses of 50 – 2000 fs duration. Our measurements show evidence for an unexpectedly low laser intensity threshold: ~ 3 1015 W/cm2 at 60 fs and ~ 3 1014 W/cm2 at 610 fs. The set of data and the behavior of x-ray yields with the physical parameters explored will be presented and discussed in the light of new theoretical developments. (*) Experiments are performed on the LUCA (Laser Ultra Court Accordable) in Saclay, France.

International audience

Interaction of high intensity ultrashort laser pulses with matter has received considerable attention in the last few years. With clusters in intense optical fields (F > 109 V/cm), the energy coupling between radiation and matter is extremely efficient, providing specific features that are not observed when atoms, small molecules or even solid are used as targets : multicharged ions reaching the MeV, hot electrons up to few keV and keV x-ray photons are produced in the laser heated cluster plasma. Here, we focus on the x-ray generation related to the production of highly stripped and excited ions. We study deexcitation of species from Ar12+ to Ar16+ with K vacancy for Ar clusters and from Xe24+ to Xe34+ with L vacancies for Xe clusters. The goal is to understand how electrons initially produced by Optical Field Ionisation (OFI) can reach enough energy to generate a strong production of ions with inner shell vacancies. We have performed quantitative studies(*) on the evolution of absolute photon emission yields and complete charge state distributions with different physical parameters governing the interaction ; namely intensity, polarization, pulse duration and wavelength of the laser, size and atomic number of the clusters. KeV x-rays are studied from rare-gas clusters irradiated with intense (I ~ 1014–1018 W cm-2) infrared and blue laser pulses of 50 – 2000 fs duration. Our measurements give rise to fundamental results like an optimum heating time in the x-ray production and an intensity threshold unexpectedly low (~ 1015 W/cm2 at 50 fs and ~ 2 1014 W/cm2 at 575 fs). The set of data and the behavior of x-ray yields with the physical parameters explored will be presented and discussed. (*) Experiments are performed on the LUCA (Laser Ultra Court Accordable) in Saclay, France.

Absolute Ar XK (3 keV) and Xe XL (4 keV) photon yields are measured as a function of laser peak intensity, for large (104 - 105 atoms) argon and xenon clusters submitted to intense laser pulses. A clear threshold behavior is observed. The intensity threshold is found as low as 2 1014 Wcm-2, a value matching the production of singly-charged argon or doubly-charged xenon by optical field ionization. Possible mechanisms involved in the inner-shell ionization are discussed. The outcome on the optimization of keV X-ray production is underlined., Comment: 1 table, 4 figures. submitted to Physical Review Letters

Interaction of high intensity ultrashort laser pulses with matter has received considerable attention in the last few years. With clusters in intense optical fields (F > 109 V/cm), the energy coupling between radiation and matter is extremely efficient, providing specific features that are not observed when atoms, small molecules or even solid are used as targets : multicharged ions reaching the MeV, hot electrons up to few keV and keV x-ray photons are produced in the laser heated cluster plasma. Here, we focus on the x-ray generation related to the production of highly stripped and excited ions. We study deexcitation of species from Ar12+ to Ar16+ with K vacancy for Ar clusters and from Xe24+ to Xe34+ with L vacancies for Xe clusters. The goal is to understand how electrons initially produced by Optical Field Ionization (OFI) can reach enough energy to generate a strong production of ions with inner shell vacancies. We have performed quantitative studies(*) on the evolution of absolute photon emission yields and complete charge state distributions with different physical parameters governing the interaction ; namely intensity, polarization, pulse duration and wavelength of the laser, size and density of the clusters. KeV x-rays are studied from rare-gas clusters irradiated with intense (I ~ 1014–1018 W cm-2) infrared and blue laser pulses of 50 – 2000 fs duration. Our measurements give rise to fundamental results like an optimum heating time in the x-ray production and an intensity threshold unexpectedly low (~ 1015 W/cm2 at 50 fs and ~ 2 1014 W/cm2 at 575 fs). The set of data and the behavior of x-ray yields with physical parameters will be presented and discussed. (*) Experiments are performed on the LUCA (Laser Ultra Court Accordable) in Saclay.

Tout comme l'interaction d'ions multichargés avec la matière, des impulsions laser (d'une durée comprise entre 50 fs et 1ps) de très haute intensité ( Ilaser > 1017 W/cm2 soit un champ électrique > 109 V/cm) induisent une excitation électronique extrêmement intense de la cible. En particulier, il a été observé expérimentalement que l'interaction d'un faisceau laser femtoseconde de grande puissance avec un jet d'agrégats de gaz rare ([Ar]n, [Kr]n ou [Xe]n avec n compris entre 104 et 106) conduit à la production d'ions fortement multichargés (Xe30+ par exemple), à l'éjection d'électrons très énergétiques (jusqu'à Ecin ~ 3 keV) ou bien encore à la génération de rayons X durs (EhΝ > keV). L'ensemble de ces résultats expérimentaux tend finalement à prouver l'existence d'un très fort couplage énergétique entre le rayonnement électromagnétique incident et ces nano objets, beaucoup plus important que ce qui est observé pour une cible atomique (jet gazeux) voire une cible solide. Alors que de nombreuses équipes à travers le monde se sont principalement intéressées à l'étude de la production ionique, nous avons, en ce qui nous concerne, étudié précisément et quantitativement le rayonnement X issu de cette interaction tout en contrôlant au mieux l'ensemble des paramètres physiques gouvernant l'interaction (intensité laser, durée d'impulsion, longueur d'onde ou polarisation du laser, taille et densité des agrégats ...). Il sera donc présenté et discuté lors de ce séminaire les principaux résultats expérimentaux que nous avons obtenus lors de diverses campagnes d'expériences réalisées auprès du Laser Ultra Court Accordable du SPAM au CEA / Saclay.

International audience; The interaction between short laser pulses (electric field > 109 V/m) and Van Der Waals clusters induces an intense electronic excitation of the matter. In particular, the energy coupling between the radiation and the matter is much more efficient than for atomic or solid targets. Experimentally, highly charged ions (like Xe40+), energetic electrons (with Ekin > 3keV) and keV x-rays have been observed. Whereas many studies concentrated on ion emission yields [1], we are interested on the x-ray production (E > 1 keV) when large rare gas cluster ((Ar)n, (Kr)n and (Xe)n with n>104 atoms/cluster) are submitted to intense (up to 5 1017 W/cm2) ultra - short (50 fs to 1 ps) laser pulses (IR-800 nm or UV-400 nm). The x-rays observed are emitted by highly charged ions: for example, from Ar11+ to Ar16+ with K vacancies in the case of Ar clusters [2] and from Xeq+ with q " 24 with L vacancies in the case of xenon. Our goal is to understand how electrons initially produced by optical field ionisation can reach enough energy to generate a strong production of ions with inner shell vacancies. Because the heating mechanisms involved remain controversial, we perform studies, under well-controlled conditions, on the evolution of the absolute photon emission yields and the complete charge state distribution with different physical parameters governing the interaction (like intensity, polarization, and wavelength of the laser, size and density of the clusters). A set of experimental data will be presented and discussed. References [1] Ditmire et al., Phys. Rev. A 53 (1996) 3379. [2] Lamour et al., Proc. of SPIE 4504 (2001) 97 and Rozet et al Physica Scripta T92 (2001) 113. [3] Adoui et al NIM B 205 (2003) 341.

International audience; Atomic physics experiments, dedicated to the study of the production and the transport of projectile excited states have been performed for different systems, in the regime of high to intermediate velocity, using the GANIL facilities in Caen (France). High-resolution x-ray spectroscopy has been applied to probe the earlier first stage of ion-solid interaction from a very short time scale (10-15 s), corresponding to single collision conditions, up to equilibrium [1,3]. These experiments have allowed to test the production and the transport of projectile excited states with different degrees of sensitivity to either individual collision processes (the collisional part) and/or to the dynamical screening associated to the wake field induced in the medium by the passage of the projectile. These two competing processes have not the same time scale and do not lead to the same effects on the projectile excited state populations. In parallel, two types of ion transport description have been developed, which take into account both aspects of the target response but with different approximations. One is a quantum mechanical approach, solving a set of master equations [2, 3, 5]. The second is based on a Monte Carlo simulation and can be performed using both classical and quantum approaches in the calculation [4-7]. Comparison with theories will be presented, and the validity of the approximations done in the two different approaches will be discussed. 1. Vernhet D et al 1998 J. Phys. B. 31, 117-119 2. Rozet J-P et al 1999 J. Phys. B. 32, 4677-4696 3. Vernhet D et al 2000 AIP 500, 666-676 4. Reinhold C. O. et al 2000 J. Phys. B 33, L111-L117 5. Vernhet D et al 2001 Physica Scripta T92, 233-236 6. Minami T et al 2002 Phys. Rev. A 65, 032901,1-11 7. Minami T et al 2003 NIM B 205, 818-825

Chair of the conference and Editor of the special issue vol 205, n°11

CAS, BIAS; pas de résumé

The availability of high-performance ion storage rings, of swift ion and cluster accelerators producing intense beams with excellent optical quality and of ion sources providing highly charged slow ions, have enabled a series of benchmark experiments on particle – matter collisions. In addition, developments in target preparation techniques along with significant advances in large area many-particle detection devices of extreme spatial and time resolution have allowed to study in detail the dynamics of collision products. The whole research activity in this field covers a wide range of scientific topics: New generation of prominent experiments concerns the interaction of atomic, molecular or cluster ions, over a large range of energy (from eV to GeV), with matter – matter including namely electrons, plasmas, atoms, molecules, clusters and solids. Nowadays, in many cases, both the states of these incoming ions and the response of the target are characterised during the collision. The fundamental goal is to probe the response of matter under the influence of strong and short pulses of electromagnetic radiation. For collisions with dilute media, high precision measurements of multiple processes cross sections are at hand and reveal shortcomings of the most sophisticated theories. The knowledge acquired on elementary process has opened the way to the investigation of the dynamics of more complex systems, like induced fragmentation of molecules or clusters. Ions interaction with electrons shows up new states of atoms, molecules and clusters. Beside the prime importance of electron-ion collisions in plasmas directly related to heavy ion inertial fusion purposes, resonances in collision cross sections provide today an alternative access to highly accurate information on atomic energy levels, and therefore a sensitive test of QED calculations (link with section 2). Finally, mechanisms responsible for strong energy deposition during ion interaction with condensed matter (bulk and surface) are determined within deep insight. These studies clearly provide crucial information for the understanding of the first stages of material modifications discussed in section 4. Beyond its own fundamental interest, the field of ion-matter interaction has also a strong impact on many other scientific domains like astrophysics and astrochemistry, atmospheric physics, radiobiology and radiation chemistry.

The population dynamics of the internal state of 60 MeV/u Kr35+ ions traversing amorphous carbon foils is studied theoretically and experimentally. This system is of particular interest as the times scales for collisional distribution, mixing due to the wake field, and radiative processes are comparable to each other. A transport theory based on a quantum-trajectory Monte Carlo method is developed, which treats the collisional and radiative redistribution of states on the same footing. The simulations exhibit clear signatures for the interplay between radiative decay and collisional mixing. Good agreement with experimental data is found.

International audience

International audience; We have performed studies of keV X-ray production from (Ar)n , (Kr)n and (Xe)n rare gas clusters (with n between 104 and 106 atoms/cluster) submitted to intense (~10^18 W/cm2) infrared (800 nm) laser pulses. Up to 10^6 3 keV photons per pulse at a moderate (~10^15/cm3) atomic density have been observed. High resolution spectroscopy studies in the case of (Ar)n clusters have also been performed, giving unambiguous evidence of highly charged (up to heliumlike) ions with K vacancies production. We have determined the photon energies and the absolute photon emission yields as a function of several physical parameters governing the interaction : size and atomic number of the clusters, peak intensity of the laser. Unexpectedly low laser intensity thresholds (~10^15Wcm-2) have been measured. The results obtained indicate nevertheless that X-rays may be emitted before cluster explosion on a subpicosecond time scale, and that several mechanisms must be involved in the first stage of the production of the hot nanoplasma induced from each cluster.

Performed studies of keV X-ray production from (Ar)n, (Kr)n and (Xe)n rare gas clusters (with n between 104 and 106 atoms/cluster) submitted to intense (18 W/cm2) infrared (800 nm) laser pulses. Up to 106 3 keV photons per pulse at a moderate (1015/cm3) atomic density have been observed. High resolution spectroscopy studies in the case of (Ar)n clusters have also been performed, giving unambiguous evidence of highly charge (up to heliumlike) ions with K vacancies production. We have determined the photon energies and the absolute photon emission yields as a function of several physical parameters governing the interaction: size and atomic number of the clusters, peak intensity of the laser. Unexpectedly low laser intensity thresholds ( approximately=1015 Wcm-2) have been measured. The result obtained indicate nevertheless that X-rays may be emitted before cluster explosion on a subpicosecond time scale, and that several mechanisms must be involved in the first stage of the production of the hot nanoplasma induced from each cluster

International audience; We have performed studies of keV x-ray production from (Ar)n , (Kr)n and (Xe)n rare gas clusters (with n between 104 and 106 atoms/cluster) submitted to intense (~10^18 W/cm2) infrared (790 nm) laser pulses. We have determined the photon energies and the absolute photon emission yields as a function of several physical parameters governing the interaction : size and atomic number of the clusters, peak intensity of the laser. Up to 10^6 3 keV photons per pulse at a moderate (10^15/cm3) atomic density have been observed. High resolution spectroscopy studies in the case of (Ar)n clusters have also been performed, giving unambiguous evidence of highly charged (up to heliumlike) ions with K vacancies production. The results obtained indicate that X-rays are emitted before cluster explosion on a subpicosecond time scale, and shed some light on the mechanisms involved in the first stage of the production of the nanoplasma induced from each cluster.