Energy loss of protons in W using fully relativistic calculations and mean excitation energies of W, Au, Pb, and Bi

We present a theoretical study on the energy loss of protons in wolframium by calculating target fully relativistic wave functions and binding energies. The HULLAC code is employed to obtain numerical solutions of the Dirac equation. We use the shellwise local plasma approximation (SLPA) to evaluate...

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Detalles Bibliográficos
Autores principales: Montanari, Claudia Carmen, Mitnik, Dario Marcelo, Archubi, Claudio Dario, Miraglia, Jorge Esteban
Publicado: 2009
Materias:
4f-electrons
Cross section
Dirac equations
Energy loss
Energy regions
Experimental data
Fully relativistic calculations
Impact energy
Mean excitation energy
Numerical solution
Subshells
Target electrons
Theoretical study
Very high energies
Binding sites
Electron energy loss spectroscopy
Electrons
Energy dissipation
Excitation energy
Lead
Lead alloys
Linear equations
Nuclear energy
Potential energy
Protons
Tungsten
Wave functions
Binding energy
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10502947_v80_n1_p_Montanari
http://hdl.handle.net/20.500.12110/paper_10502947_v80_n1_p_Montanari
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:We present a theoretical study on the energy loss of protons in wolframium by calculating target fully relativistic wave functions and binding energies. The HULLAC code is employed to obtain numerical solutions of the Dirac equation. We use the shellwise local plasma approximation (SLPA) to evaluate the different moments of the energy loss. The partial contribution of each subshell of target electrons is calculated separately, including the screening among the electrons of the same binding energy. We pay special attention to the role of the outer 4f shell and the screening between electrons of near subshells (i.e., the 5p and 4f electrons). Results for stopping and straggling cross sections are compared to the experimental data available. Our calculations describe rather well the stopping measurements around the maximum and for very high energies, but overestimate the data for impact energies around 1MeV. We find that the SLPA results tend clearly to Bethe limit, but show a systematic overestimation in the energy region of 1-2 MeV. This overestimation may indicate the presence of other mechanisms included neither in the SLPA nor in Bethe formulations. We also present results for the stopping number of W, Au, Pb, and Bi which follow quite well the Lindhard scaling. A theoretical mean excitation energy I (W) =710eV is obtained, in good agreement with the suggested value of 727±30eV. Theoretical mean excitation energies for Au, Pb, and Bi are also presented, which are in good agreement with the experimental ones. © 2009 The American Physical Society.

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