Energy loss of protons in Au, Pb, and Bi using relativistic wave functions

C. C. MONTANARI; C. D. ARCHUBI; D. M. MITNIK; J. E. MIRAGLIA

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

American Physical Society

Año: 2009 vol. 79 p. 3290301 - 3290310

1050-2947

We present a theoretical study on proton energy loss in solid targets of atomic number greater than 54. Fully-relativistic wave functions and binding energies are obtained by solving numerically the Dirac equation. Ab initio calculations are developed for the first (stopping) and second (straggling) moments of the energy transferred from the ion to the target electrons. The Shellwise Local Plasma Approximation (SLPA) is employed for the inner-shells, and the Mermin dielectric function for the valence electrons. The dielectric response of each sub-shell is calculated separately, including in this way the screening among the electrons of the same binding energy. Results for stopping and straggling cross sections of protons in Au, Pb and Bi are compared with the available experimental data. The theoretical stopping results are very good in the case of Au, reproducing the experimental data in an extensive energy region (10keV-100MeV). For Pb and Bi, the stopping results agree with the measurements for energies above 300 keV, for which the inner-shells play a major role. However, we found some difficulties around the stopping maximum. For the energy loss straggling, we obtained reasonably good agreement with the experiments for the three targets studied.