  Recently, a series of dedicated inverse-kinematics experiments performed at
GSI, Darmstadt, has brought an important progress in our understanding of
proton and heavy-ion induced reactions at relativistic energies. The nuclear
reaction code ABRABLA that has been developed and benchmarked against the
results of these experiments has been used to calculate nuclide production
cross sections at different energies and with different targets and beams.
These calculations are used to estimate nuclide production rates by protons in
thick targets, taking into account the energy loss and the attenuation of the
proton beam in the target, as well as the low-energy fission induced by the
secondary neutrons. The results are compared to the yields of isotopes of
various elements obtained from different targets at CERN-ISOLDE with 600 MeV
protons, and the overall extraction efficiencies are deduced. The dependence of
these extraction efficiencies on the nuclide half-life is found to follow a
simple pattern in many different cases. A simple function is proposed to
parameterize this behavior in a way that quantifies the essential properties of
the extraction efficiency for the element and the target - ion-source system in
question.
