Phase effect in stopping of H ions in Mg
| Autor: | R. Díez Muiño, G. Schrenk, M. Bergsmann, Andrés Arnau, W. Raab, A. Salin, Pedro M. Echenique, F. Kastner, Peter Bauer |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Physical Review B. 62:3153-3159 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.62.3153 |
| Popis: | We present measurements and calculations of electronic stopping of protons and deuterons in Mg (gas and solid) in the range 15--650 keV/A. The measurements were performed by transmitting the ion beam through a vapor cell containing solid and gaseous Mg in thermal equilibrium. In order to get absolute values of the stopping cross section \ensuremath{\varepsilon}, the experimental gas data were normalized by the requirement that the experimental phase effect $\ensuremath{\Delta}\ensuremath{\varepsilon}\ensuremath{\equiv}{\ensuremath{\varepsilon}}_{\mathrm{gas}}\ensuremath{-}{\ensuremath{\varepsilon}}_{\mathrm{solid}}$ ---with the \ensuremath{\varepsilon} for metallic Mg from Bergsmann (1998)--- is equal to the theoretical value $\ensuremath{\Delta}{\ensuremath{\varepsilon}}_{\mathrm{th}}$ at a reference energy of 400 keV. We have used a Hartree-Fock-Slater description of the Mg atom and the first Born approximation to calculate excitation and ionization of Mg in the gas phase and the ionization of the inner shells of solid Mg, while the valence electrons $(3s)$ of solid Mg are described by a free-electron gas. Charge-exchange processes are explicitly taken into account to estimate both the equilibrium charge state fractions and the energy loss in charge-exchange processes, as required by our charge state approach. We obtain a pronounced phase effect of up to 70% at 20 keV. Theory and experiment coincide within the experimental uncertainties in a wide energy range; systematic deviations occur only at low energies where the linear model breaks down. |
| Databáze: | OpenAIRE |
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