Swift Heavy Ion Induced Electron Emission from Solids

Quite a number of experiments have been performed on electron emission from solids induced by slow (projectile velocity Vp \u3c 1 atomic unit) or medium velocity heavy ions (projectile energy Ep \u3c 1 MeV/u). Only a few experiments have been made with fast heavy ions (projectile atomic number Zp \u3e 8, Ep \u3e 2 MeV/u) concerning either electron emission yields -y, or double differential electron energy spectra d2n(0)/dEd0 as a function of the observation angle 0. We present the results obtained so far on electron emission induced by fast (Ep \u3e 2 MeV/u) heavy ions (Zp ~ 6). Topics discussed include experimental results for electron yields, -energy and -angular distributions and channelling phenomena as well as the theoretical approaches. We also present new results from recent studies on the evolution of electron yields and doubly differential electron spectra with target thickness for Ar (13.6 MeV/u) obtained at GANIL (the french heavy ion accelerator Grand Accelerateur National d\u27Ions Lourds )

Radiolysis of Amino Acids by Heavy and Energetic Cosmic Ray Analogs in Simulated Space Environments: α\alpha-Glycine Zwitterion Form

In this work, we studied the stability of the glycine molecule in the crystalline zwitterion form, known as {\alpha}-glycine ($^{+}$NH$_{3}$CH$_{2}$COO$^{-}$) under action of heavy cosmic ray analogs. The experiments were conducted in a high vacuum chamber at heavy ions accelerator GANIL, in Caen, France. The samples were bombarded at two temperatures (14 K and 300 K) by $^{58}$Ni$^{11+}$ ions of 46 MeV until the final fluence of $10^{13}$ ions cm$^{-2}$. The chemical evolution of the sample was evaluated in-situ using Fourrier Transformed Infrared (FTIR) spectrometer. The bombardment at 14 K produced several daughter species such as OCN$^-$, CO, CO$_2$, and CN$^-$. The results also suggest the appearing of peptide bonds during irradiation but this must be confirmed by further experiments. The halflives of glycine in Interstellar Medium were estimated to be 7.8 $\times 10^3$ years (300 K) and 2.8 $\times 10^3$ years (14 K). In the Solar System the values were 8.4 $\times 10^2$ years (300 K) and 3.6 $\times 10^3$ years (14 K). It is believed that glycine could be present in space environments that suffered aqueous changes such as the interior of comets, meteorites and planetesimals. This molecule is present in proteins of all alive beings. So, studying its stability in these environments provides further understanding about the role of this specie in the prebiotic chemistry on Earth.Comment: 28 pages, 12 figures, 9 tables. Accepted to be published at Monthly Notices of the Royal Astronomical Society (MNRAS

Production of Oxidants by Ion Bombardment of Icy Moons in the Outer Solar System

Our groups in Brazil, France and Italy have been active, among others in the world, in performing experiments on physical-chemical effects induced by fast ions colliding with solids (frozen gases, carbonaceous and organic materials, silicates, etc.) of astrophysical interest. The used ions span a very large range of energies, from a few keV to hundreds MeV. Here we present a summary of the results obtained so far on the formation of oxidants (hydrogen peroxide and ozone) after ion irradiation of frozen water, carbon dioxide and their mixtures. Irradiation of pure water ice produces hydrogen peroxide whatever is the used ion and at different temperatures. Irradiation of carbon dioxide and water frozen mixtures result in the production of molecules among which hydrogen peroxide and ozone. The experimental results are discussed in the light of the relevance they have to support the presence of an energy source for biosphere on Europa and other icy moons in the outer Solar System.This research has been supported by the European COST Action CM0805: The Chemical Cosmos.Boduch, P.; Da Silveira, EF.; Domaracka, A.; Gomis Hilario, O.; Lv, XY.; Palumbo, ME.; Pilling, S.... (2011). Production of Oxidants by Ion Bombardment of Icy Moons in the Outer Solar System. Advances in Astronomy. 1-10. doi:10.1155/2011/327641S11

Interaction ions-surfaces (étude de la pulvérisation du fluorure de lithium LiF par technique d imagerie XY-TOF-SIMS)

Le dépôt d énergie cinétique d un projectile rapide dans une cible conduit à l éjection de matière sous forme d atomes ou d agrégats ( pulvérisation ). La mesure des rendements, des distributions en énergie et en angle des particules pulvérisées contribuent à comprendre le processus microscopique de l endommagement et de la création de défauts dans les matériaux. Un nouveau dispositif expérimental ultra vide (AODO) permet de mesurer les distributions en masse et les vecteurs vitesse de chaque ion secondaire émis par technique d imagerie XY-TOF-SIMS ( Secondary Ion Mass Spectroscopy ). Ici, nous nous intéressons à la pulvérisation du fluorure de lithium (isolant cristallin modèle à gap très important 14 eV) irradié par des ions lourds rapides ( 10 MeV/u). En fonction du pouvoir d arrêt Se, deux régimes de l évolution des rendements de pulvérisation Y des ions secondaires sont observés. Pour les faibles Se ( 8 keV/nm), régime de forte perturbation, une saturation (Y = constante) est observée. Les données expérimentales permettent aussi de tester des modèles théoriques proposés dans la littérature (le modèle de l onde de choc, pointe thermique, explosion coulombienne ). Il apparaît qu aucun de ces modèles ne peut interpréter correctement l ensemble de ces résultats. Une distribution de type Maxwell-Boltzmann décrit bien les distributions en énergie des ions secondaires. Les processus générant la pulvérisation doivent donc être principalement d origine thermique.The deposition of energy lost by a fast ionic projectile in the target leads to the ejection of material in the form of atoms or clusters ( sputtering ). The measurements of yields, energy and angular distributions of sputtered particles contribute to the understanding of the initial microscopic processes of damage and defect creation in materials. A new UHV system (AODO) allows measuring the mass distributions and the velocity vectors of each emitted secondary ion by means of time-of-flight and imaging techniques XY-TOF-SIMS ( Secondary Ion Mass Spectroscopy ) with well prepared target surfaces. Here, we focus on the sputtering of lithium fluoride (an ionic crystal, a large band gap insulator 14 eV) by fast heavy ions ( 10 MeV/u). As a function of the electronic stopping power Se, two regimes for the evolution of secondary ions yield Y with Se are observed. At low Se ( 8 keV/nm), strong perturbation regime, a saturation Y = constant is observed. The experimental data permit also to test the theoretical models existing in the literature (for example: shock wave model, thermal spike, Coulomb explosion ...). It appears that none of these models can correctly describe the ensemble of the experimental observations. However, the Maxwell-Boltzmann distribution describes the energy distributions of the emitted ions. This gives us a possible indication that the processes generating the sputtering could be mainly of thermal origin.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Editorial - Swift Heavy Ions in Matter

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CIRIL: Interdisciplinary Research at GANIL

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Three-Electron Auger Process from Beam-Foil Excited Multiply Charged Ions

Electron emission from collisions of C3+ ions (22.7 AMeV) with carbon foils (21, 49 and 90 μg/cm2) was studied by the time-of-flight method. Two prominent emission patterns can be readily identified as ‘‘binary encounter'' electrons and ‘‘cusp'' electrons. With the thinnest target only, a third structure is visible at slightly lower time-of-flight (thus slightly higher energy) than the cusp electrons. The energy of these electrons would correspond to 647+116-104 eV if they were emitted from the projectile frame of reference. A possible explanation is a rare three-electron-Auger K2L2L1 process

CIRIL: Interdisciplinary Research at GANIL

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Editorial

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Electron emission induced by H+ and H0 incident on thin carbon foils: Influence of charge changing processes

The forward and backward electron emission yields γF and γB have been calculated by Monte Carlo simulation for protons (H+) and hydrogen atoms (H0) (with energies between 25 keV and 5 MeV) incident on thin amorphous carbon foils. Direct electron excitations by the incident projectiles as well as electron excitations resulting from charge exchange processes undergone by H+ or H0 have been taken into account. For the latter, Auger and Shell processes have been considered. Subsequent electron transport has been considered in order to calculate the forward and backward electron emission yields γF and γB. © 2004 Elsevier B.V. All rithts reserved.SCOPUS: cp.jinfo:eu-repo/semantics/publishe