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

AMER PHYSICAL SOC

Año: 2009 vol. 79 p. 32903 - 32910

1050-2947

We present a theoretical study on the energy loss by protons in solid targets of atomic numbergreater than 54. Fully-relativistic wave functions and binding energies are calculated by solvingnumerically the Dirac equation. First (stopping) and second (straggling) moments of the energytransfered from the ion to the target electrons, are calculated. The Shellwise Local Plasma Approximation(SLPA) is employed for the inner-shells, and the Mermin dielectric function for the valenceelectrons. The dielectric response of each shell is calculated separately, including in this way thescreening among the electrons of the same binding energy.Results for stopping and straggling cross sections of protons in Au, Pb and Bi are comparedwith the available experimental data. Stopping results are good, spetially in gold, reproducing theexperimental data in an extensive energy region (5keV-100MeV). For the energy loss straggling,we obtain the asymptotic tendency towards Bohr high energy limit proportional to ZT (all targetelectrons active). We also obtain a similar tendency for the energy loss straggling of each shellproportional to the number of electrons in the shell.