  Equilibrium charge state distributions of stable 60Ni, 59Co, and 63Cu beams
passing through a 1um thick Mo foil were measured at beam energies of 1.84
MeV/u, 2.09 MeV/u, and 2.11 MeV/u respectively. A 1-D position sensitive
Parallel Grid Avalanche Counter detector (PGAC) was used at the exit of a
spectrograph magnet, enabling us to measure the intensity of several charge
states simultaneously. The number of charge states measured for each beam
constituted more than 99% of the total equilibrium charge state distribution
for that elements. Currently, little experimental data exists for equilibrium
charge state distributions for heavy ions with 19<Zp,Zt<54 (Zp and Zt, are the
projectile's and target's atomic numbers respectively). Hence the success of
the semi-empirical models in predicting typical characteristics of equilibrium
CSDs (mean charge states and distribution widths), has not been thoroughly
tested at the energy region of interest. A number of semi-empirical models from
the literature were evaluated in this study, regarding their ability to
reproduce the characteristics of the measured charge state distributions. The
evaluated models were selected from the literature based on whether they are
suitable for the given range of atomic numbers and on their frequent use by the
nuclear physics community. Finally, an attempt was made to combine model
predictions for the mean charge state, the distribution width and the
distribution shape, to come up with a more reliable model. We discuss this new
"combinatorial" prescription and compare its results with our experimental data
and with calculations using the other semi-empirical models studied in this
work.
