[en] We have investigated the effect of the reaction window for the energy deposition in molecules or clusters with various projectiles (H⁺, F⁺, Cl⁺) in collision induced dissociation under energy control (CIDEC). The formation dynamics of scattered negative ions in such collision is discussed. We have measured the production rate of Cl^- ions in Cl⁺ + C₆₀ collisions at 18 keV to be 4%. This rate is compared to previous results obtained with F^q+ (q=1-3) projectile ions. The CIDEC method has been extended to neutral projectiles (F⁰) and we report on the choice of the projectile to control the amount of the energy deposited in the molecules or the clusters. Results on the excitation energy distributions of C₆₀⁺ and C₆₀²⁺ are presented.

[en] We report experiments using a small electrostatic ion storage ring. We demonstrate its capability to measure the lifetime of metastable anions and cations up to hundred of milliseconds produced in the ECR source. First experiments using LASER heating are also presented.

[en] We have built a new small electrostatic ion storage ring, the so-called mini-ring, in order to store ion beams for long durations (up to seconds) using a limited number of electrodes in limited space. In this paper, we demonstrate the capability of the mini-ring to store ions on a rather long time scale (100 ms) limited by collisions on the background gas. We also show that by measuring the frequency of ion motion around the ring, we can use the mini-ring as an energy analyzer to determine the energy loss of F^- anions produced in the double electron transfer process in 4 keV F⁺-Ar collisions.

[en] The excitation and dissociation processes of the molecule W(CO)₆ in collisions with low kinetic energy (3keV) protons, monocharged fluorine and chlorine ions has been studied using double charge transfer spectroscopy. Based on the experimental data, the emission of the first CO is tentatively attributed to a non-statistical direct dissociation process whereas the emission of the second or more CO ligands is attributed to the statistical dissociation processes.

[en] The production rate of negative ions in collisions between neutral, singly and multiply charged ions with clusters or small molecules is a crucial parameter to study the fragmentation of the targets as a function of the excitation energy (CIDEC method). We report on high production yields of negative ions in collisions between F''q''+(q = 1-3) ions and fullerene C₆₀ and adenine molecules. The dynamics of the formation of the negative ion in such collisions is discussed.

[en] Processes in atoms or molecules on the attosecond timescale have been measured using XUV attosecond and IR femtosecond pulses overlapping in time and controlled with attosecond accuracy. Within this general framework, many strategies have been developed using the harmonics of the fundamental pulse. In this paper, we focus on a specific configuration where the attosecond pulse train is composed by odd harmonics and is dressed by the second harmonic of the fundamental light. Measuring the angularly resolved photoelectron spectrum as a function of the delay between the pulses, a clear oscillation of the anisotropy parameters appears revealing attosecond controlled interferences. This process, is assigned to interferences between two quantum paths involving one XUV photon, on one path, and a XUV+UV photons on the other path. The XUV-UV delay dependent up–down asymmetry can be interpreted following the usual RABBITT formalism, where the dressing photon energy corresponds to the energy separation between the XUV photons of the attosecond pulse train. This approach allows an intuitive analysis of the interference and provides a well suited method for the study of complex valence band systems thanks to the limited congestion of the resulting spectrum. (paper)

[en] In this paper we discuss the production of molecular PAH cations using an ECR ion source and their subsequent cooling studied with an electrostatic storage ring, the Mini-Ring on a time range up to 10 ms. We show that the ECR ion source can produce high currents of small PAH cation, here naphthalene and anthracene cations. Then, we report experimental result for the cooling of three PAH cations (anthracene, naphthalene and pyrene) stored in our compact electrostatic storage ring (the Mini-Ring). We show that the Poincaré recurrent fluorescence plays a major role in the cooling process of those PAH cations. We show that for a given internal energy, the cooling rate is much smaller for pyrene than for anthracene and naphthalene. We conclude that the Poincaré recurrent fluorescence is less efficient due to smaller oscillator strength of the D₂-D₀ electronic transition for pyrene.

[en] We report on the commissioning of an electrostatic ion storage ring of small dimensions, the so-called Mini-Ring. We demonstrate its capability to store ion beam for up to tens of milliseconds.

[en] An experiment is described in which an apparatus is used to demonstrate the feasibility of measuring multiphoton photoionization rates in the interaction of short pulsed lasers with atoms or molecules. With this methodology, the ionization rate is measured as a function of the spatial position in the beam-waist region of the laser through the direct three-dimensional spatial imaging of the ionization events. Thus, if the spatial dependence of the laser beam intensity were known, a series of experiments could yield the intensity dependence of multiphoton ionization without the assumptions or errors that are generally inherent in the integration over one or more dimensions in the laser focal volume