Download or read book Etude exp rimentale des transferts de charge dans les interactions d ions avec des surfaces d halog nures alcalins written by Sai͏̈d Abidi and published by . This book was released on 2000 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: CE TRAVAIL DE THESE PORTE SUR L'ETUDE EXPERIMENTALE DES TRANSFERTS DE CHARGE LORS DES INTERACTIONS D'IONS MONOCHARGES DE QUELQUES KILOELECTRONVOLTS AVEC DES SURFACES D'HALOGENURES ALCALINS. DES IONS DE GAZ RARES, ALCALINS ET DES IONS REACTIFS ONT ETE UTILISES. CE TRAVAIL COMPORTE TROIS PARTIES. DANS LA PREMIERE NOUS AVONS ETUDIE LA DIFFUSION D'IONS HE +, NE + ET NA + EN INCIDENCE RASANTE SUR UNE SURFACE DE CHLORURE DE SODIUM. POUR LES IONS DE GAZ RARES NOUS AVONS MESURE DES FRACTIONS D'IONS POSITIFS TRES FAIBLES, LA NEUTRALISATION AUGER ETANT TRES EFFICACE POUR CE TYPE D'IONS. UN MECANISME DE RE-IONISATION AU COURS DE LA COLLISION VIOLENTE EST RESPONSABLE DE L'AUGMENTATION DE LA FRACTION D'IONS POSITIFS AVEC L'ANGLE DE DIFFUSION. DANS LE CAS DU SODIUM, LA PROBABILITE DE SURVIE DES IONS EST TRES ELEVEE. NOUS AVONS SUGGERE QUE LA FAIBLE NEUTRALISATION DES IONS NA + SE PRODUIT AU COURS DE LA COLLISION PROCHE SUR LES SITES DE LA SURFACE. DANS LA DEUXIEME PARTIE ON S'EST INTERESSE A LA DIFFUSION D'IONS REACTIFS (H +, O + ET F +) DANS DES CONFIGURATIONS DE COLLISIONS RASANTES, ET PLUS PARTICULIEREMENT A LA PRODUCTION D'IONS NEGATIFS LORS DE L'INTERACTION. LES FRACTIONS D'IONS NEGATIFS MESUREES SONT TRES ELEVEES, NOUS AVONS LIE CECI AUX PROPRIETES ELECTRONIQUES DE LA SURFACE QUI PERMETTENT UN MECANISME SEQUENTIEL DE CAPTURE ET DE PERTE D'ELECTRONS LE LONG DE LA TRAJECTOIRE DE L'ION. DANS LA DERNIERE PARTIE DE CE TRAVAIL NOUS AVONS ETENDU CETTE ETUDE AUX CAS DES INTERACTIONS A GRANDS ANGLES. CETTE ETUDE A ETE MENEE AVEC DES IONS F +, NE + ET NA +. L'ANALYSE AZIMUTALE DES FRACTIONS DE CHARGE MONTRE L'EFFET DES TRAJECTOIRES SUR LES PROCESSUS D'ECHANGE DE CHARGE. EN PARTICULIER L'ETUDE AZIMUTALE DES FRACTIONS POSITIVE ET NEGATIVE DES PARTICULES DE RECUL MET EN EVIDENCE LE ROLE DES EFFETS LOCAUX DANS LES INTERACTIONS D'IONS AVEC LES SURFACES D'ISOLANTS IONIQUES.

Download or read book Formation D ions N gatifs Par Transfert de Charge R sonant Lors de L interaction D atomes Avec Des Surfaces written by Jorge Alexandre Monteiro de Carvalho e Silva and published by . This book was released on 2003 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is devoted to investigations on the formation of negative ions during the interaction of atoms with surfaces. The subject of resonant charge transfer between an atom and a metallic surface is presented in chapter 1. Chapter 2 presents the coupled angular modes method which is used to calculate the energy and width of electronic levels of atoms interacting with a metallic surface. Chapter 3 presents a study of multielectronic effects in the formation of halogen negative ions scattered in grazing angle collisions by an aluminium surface. The results obtained compare well with experimental results when the multielectronic character of charge transfer is considered. The formation of carbon negative ions by sputtering of a graphite surface is studied in chapter 4, from the energy distribution of the ions, obtained experimentally, and from a computer simulation on the emission of sputtered atoms. A modeling of the formation and survival of the ions is attempted and the results discussed. The influence of the presence of two kinds of crystallographic defects on an aluminium surface on the charge transfer between an atom and the surface is studied theoretically in chapter 5. A vacancy on the surface doesn't seem to influence decisively the charge transfer. On the contrary, an adatom on the surface introduces a local modification of the charge transfer due to the attractif character of the potential induced by the adatom and to the existence of quasi-stationary states centred on the adatom. The non-adiabatic effects on the charge transfer between an hydrogen negative ion and the aluminium surface in the presence of an adatom are studied. Chapter 6 describes the developement of a surface analysis technique by time of flight secondary ion mass spectrometry in the multitechnique surface analysis system. The solutions adopted to pulse the primary ion beam and measure the flight time of secondary ions are described, as well as the state of advancement of this project.

Download or read book Transfert de charge sur les surfaces d argent recouvertes de chlore written by Elena Magdalena Staicu Casagrande and published by . This book was released on 2002 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents a study of changes in electron transfer processes between atomic particles and Ag(111), Ag(110) and Ag(100) surfaces exposed to chlorine. The general motivation of our study is the analyse of electronic effects in the promotion and poisoning of reactions on surfaces. Results of a study of changes in electron capture and loss rates in the interaction of fluorine, hydrogen and oxygen atoms and anions are reports for a wide range of coverages. A strong decrease is observed in the F ̄formation rates at low coverage in chemisorptions conditions on the chlorine-covered Ag(111), Ag(110) and Ag(100). The observed decrease is assigned to changes in local electronic structure at and in the vicinity of the adsorbate site and modifications in positions and widths of the anion levels. At high coverages a higher electron-capture probability is found on Ag(III), corresponding to the appearance of chlode islands. In the case of H ̄and O ̄the capture and loss rates are reported for chlorine surface Ag(111). Strong oscillatory changes in anion formation rates are observes as a function of chlorine coverage. These changes are discussed in terms of changes in local electronic structure and modifications in positions and widths of the anion levels at different phases of chlorine adsorption and in particular to interaction of the projectile with the adsorbed Cl(3p) levels. At high coverages, a higher electron capture is found, corresponding to the formation of the cristal AgCl on Ag(111). The effect of chemical environment on the neutralisation of ions with adsorbate covered surfaces was investigated in the case of H+, Ar+, Ne+ ans He+ scattered on the three surfaces exposed to chlorine. Changes in coverage in the submonolayer region of chlorine adsorption induce an non-linear oscillation of electron transfer probabilities for H+. Ar+, Ne+. This can be relates to changes in the electronic structure due to the presence of the chlorine levels. With increasing chlorine adsorption the fractions obtained on Ag(111) are affected by the appearance of chloride island on Ag(111). In the case of more highly bound He, we assigned the observed changes to modifications in quasi-resonant charge transfer rates involving the Cl(3s) level.

Download or read book Health Effects of Environmental Pollution written by and published by . This book was released on 1973 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Chemical Toxicology written by Abraham Stolman and published by Elsevier. This book was released on 2013-10-22 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress in Chemical Toxicology, Volume 5 covers topics on the improved isolation and detection procedures and quantitation methods for volatile poisons, stimulants, hallucinogenic drugs, and marihuana. The book discusses the absorption, distribution, and excretion of drugs and poisons and their metabolites; the system for the toxicological analysis of drugs in biological specimens; and the isolation and analysis of phenothiazines. The text also describes the use of fluorescence in toxicology and the toxicology of new synthetic organic polymers used in containers for food, pharmaceutical compounds, and drinkable water. Some microcrystal tests for drugs and advances in polarography as applied to toxicological analysis are also considered. Biochemists, toxicologists, and scientists involved in the study of narcotics will find the book invaluable.

Download or read book Lead Poisoning in Childhood written by Siegfried M. Pueschel and published by Brookes Publishing Company. This book was released on 1996 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: This resource examines the causes and consequences of childhood lead poisoning, offers cost-effective prevention strategies, and explores crucial legislation that can and should protect children at risk. Information on screening tests, nutrition, treatment guidelines, and safe environmental abatement techniques will help pediatricians, physicians, social workers, and nurses understand, treat, and eliminate lead poisoning in children.

Download or read book Inhaled Particles and Vapours written by British Occupational Hygiene Society and published by Pergamon. This book was released on 1961 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: