  Novel measurements of $(\alpha,\gamma)$ and $(\alpha$,n) reaction cross
sections on the target nucleus $^{151}$Eu, close to the reaction thresholds,
support the setting up of recent parameters of the $\alpha$-particle optical
model potential below the Coulomb barrier. A better understanding of the
$\alpha$-particle optical potential at these energies leads to a statistical
model analysis of additional partial cross sections that were formerly measured
but not considered within the model analysis. On this basis we have tentatively
assigned a modified $J^{\pi}$=9$^-$ spin and parity to the 22.7-h isomer in
$^{154}$Tb.
