  In order to extend the experimental database relevant for the astrophysical
gamma-process towards the unexplored heavier mass region, the cross sections of
the 151Eu(alpha,gamma)155Tb and 151Eu(alpha,n)154Tb reactions have been
measured at low energies between 12 and 17 MeV using the activation technique.
The results are compared with the predictions of statistical model calculations
and it is found that the calculations overestimate the cross sections by about
a factor of two. A sensitivity analysis shows that this discrepancy is caused
by the inadequate description of the alpha+nucleus channel. A factor of two
reduction of the reaction rate of 151Eu(alpha,gamma)155Tb in gamma-process
network calculations with respect to theoretical rates using the optical
potential by McFadden and Satchler (1966) is recommended.
