https://doi.org/10.1140/epjd/e2010-00218-1
Theoretical interpretation of equilibrium charge-state distributions of 4He ions backscattered from metallic foils using extended Bohr theory
Department of Applied Physics, Faculty of Science, Tafila Technical
University, P. O. Box 179, Tafila, 66110, Jordan
Corresponding author: a d_aamahasneh@yahoo.com
Received:
24
November
2009
Revised:
29
May
2010
Published online:
30
August
2010
Equilibrium charge-state distributions (ECSD's) for He0, He+, and
He++ backscattered by the foils made of silver have been measured using
a post-acceleration system, and simulated by the extended Bohr theory. The
kinematics behavior of the backscattered ions is understood from Rutherford
backscattering spectrometry (RBS). The results from these measurements have
been integrated with the data available in the literature to cover a wide
energy range of the incident singly charged helium ion He+. The
detected charge states increase from 0 to +Z with the incident ion energy. A
formula for calculating He0 distribution, for the studied energy range,
has been proposed. The ratio of singly to doubly ionized helium ions
backscattered from thin Ag-foils, F(He/F(He
, has been
measured as a function of incident ion velocity. The use of a semi-classical
approach, based on the theory of Bohr, allows a satisfactory theoretical
description of F(He
/F(He
ratios. It has been found that the
measured and simulated ratios are strongly decreased with the incident
velocity. The present study has demonstrated that the satisfactory fits of
ECSD's and the ratio of the fractions are mainly accounted to the
contribution of both free valance electrons of the target and screened
target nucleus in the calculation of total electron loss cross section.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010