  The formation of alpha-clusters in nuclei close to the decay thresholds is
discussed. These states can be considered to be boson-condensates, which are
formed in a second order phase transition in a mixture of nucleons and
alpha-particles. The de Broglie wavelength of the alpha-particles is larger
than the nuclear diameter, therefore the coherent properties of the
alpha-particles give particular effects for the study of such states. The
states are above the thresholds thus the enhanced emission of multiple-alphas
into the same direction is observed. The probability for the emission of
multiple-alphas is not described by Hauser-Feshbach theory for compound nucleus
decay.
