  The stopping cross sections S (E) of silicon for protons and alpha particles
have been measured over the velocity range 0.3-1.2 MeV/u from a SIMOX target
using the Rutherford Backscattering Spectrometry (RBS) with special emphasis
put on experimental aspects. A detection geometry coupling simultaneously two
solid-state Si detectors placed at 165 degrees and 150 degrees relative to each
side of the incident beam direction was used to measure the energies of the
scattered ions and determine their energy losses within the stopping medium. In
this way, the basic energy parameter, Ex, at the Si-SiO2 interface for a given
incident energy E0 is the same for ions backscattered in the two directions off
both the Si and O target elements, and systematic uncertainties in the S (E)
data mainly originating from the target thickness are significantly minimized.
A powerful computer code has been elaborated for extracting the relevant S (E)
experimental data and the associated overall uncertainty that amounts to less
than 3%. The measured S (E) data sets were found to be in fair agreement with
H. Paul compilation and with values calculated by the SRIM 06 computer code. In
the case of 4He+ ions, experimental data for the gamma-effective charge
parameter have been deduced via scaling the measured stopping cross sections to
those for protons crossing the same target at the same velocity and compared to
the predictions of the SRIM 06 code. It is found that the gamma-parameter
values generated by the latter code slightly deviate from experiment over the
velocity region around the stopping cross section maximum where strong charge
exchanges usually occur.
