Unexpected transparency in low energy Zr-90(alpha,alpha(0)) scattering andalpha-cluster structure in Mo-94 - art. no. 041601

We show that incomplete absorption in Zr-90(alpha, alpha(0)) scattering is responsible for the spectacular dip observed in the backward excitation fun ction at low energy (E-alpha approximate to 25 MeV), which we interpret as a destructive interference effect between the barrier and internal wave con tributions to the scattering amplitude. Because of this transparency, an op tical potential, which is in line with the higher energy data, can be extra cted with good accuracy. The real part of this potential is found to suppor t several rotational bands; the properties of the states of the first Pauli -allowed band, with N = 16, in particular the electromagnetic transition ra tes between the first states, are in good agreement with those of the state s of the experimental Mo-94 ground state band, suggesting that alpha-cluste r structure is still an important feature in the A = 90 region.