Laser-Induced Breakdown Spectroscopy for atmospheric monitoring of selected fine and ultrafine particles

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Tandem time-of-flight experiment for low energy collision studies

AbstractWe present an experiment adapted to collisional studies of cluster ions based on a laser vaporization setup coupled to a supersonic expansion. The ions are selected in a first time-of-flight, slowed down to the desired energy, and collided in an octopolar guide. The parent and fragment ions are then reaccelerated in order to be mass analyzed in a reflectron time-of-flight. An original method for the extraction of the ion that uses a double voltage pulse, is proposed. The experiment has been applied to collisions of hydrated cobalt ions. An absolute cross section of 17 Å2 for the loss of one water molecule by Co(H2O)2+ in collision with neon at a center-of-mass energy of 10 eV, has been determined, with an accuracy of 10%. The threshold for this reaction has been measured at 1.5 eV and is in good agreement with the existing literature (Dalleska et al. J. Am. Chem. Soc. 1994, 116, 3519). Ions that cannot be formed by conventional ligand exchange methods, can also be studied. As an example, the threshold for dehydration of the Co2(H2O)+ ion has been measured at 1.5 ± 0.2 eV

EUV and fast ion emission from cryogenic liquid jet target laser-generated plasma

A liquid jet of either nitrogen or argon of 20 mum diameter was exposed to intense laser fields with pulse durations between 70 fs and 250 ps, leading to intensities of 10(16) W cm(-2) and 10(13) W cm(-2), respectively. The emission of extreme UV light and soft X-rays shows the characteristic lines of hydrogen-like nitrogen and carbon-like argon. For nitrogen the emitted photon flux at 250 ps was about two orders of magnitude higher than for 70 fs pulses. A weak dependence on the laser polarization with respect to the liquid jet axis was found. The kinetic energy of the emitted ions easily exceeded 100 keV for nitrogen and 200 keV for argon for a pulse duration close to 2 ps

Stabilization of barium dimers on clusters: Reactions of Ba2 with Cl2 and O2 on large argon clusters

International audienceBarium dimers have been produced and stabilized by the successive pickup of two barium atoms on large argon clusters (average size of 8000). By adding chlorine and oxygen molecules, chemiluminescent reactions of these dimers have been observed. This technique of dimer formation can be extended to higher order clusters to study reactions of cold metallic clusters

Recent Progress on the Preparation of Luminescent Silicon Nanoparticles for Bio-Imaging Applications

International audienceLuminescent silicon nanoparticles particles produced by laser pyrolysis are considered as possible alternative to replace toxic Quantum Dot in bioimaging applications. However, these nanoparticles are fully oxidized when kept in water, therefore, the luminescent silicon core must be be protected from oxidation. The Si nanoparticles were embedded in monodisperse silica beads (~50 nm) produced in microemulsion. The silica beads provide protection of the silicon core and allow stability of the photoluminescence over time. They are well dispersed in water and biological medium with a colloidal stability of several days

Chemiluminescent reaction (Ba + Cl

Chemiluminescence produced by the reactive collision of barium and chlorine molecule on an 8000 argon cluster is investigated. The binary collision Ba + Cl2 on the cluster leads to the observation of the reaction intermediate BaCl2 as the dominant luminescent product whereas in the gas phase, under the single collision regime, the reaction leads exclusively to the formation of the radical pair BaCl∙ + CL This result is interpreted as a very efficient trapping of the BaCl2 intermediate by the cluster. Trapping mechanisms are discussed