  Sequences of rotational resonances (rotational bands) and corresponding
antiresonances are observed in ion collisions. In this paper we propose a
description which combines collective and single-particle features of cluster
collisions. It is shown how rotational bands emerge in many-body dynamics, when
the degeneracies proper of the harmonic oscillator spectra are removed by
adding interactions depending on the angular momentum. These interactions can
be properly introduced in connection with the exchange-forces and the
antisymmetrization, and give rise to a class of non-local potentials whose
spectral properties are analyzed in detail. In particular, we give a
classification of the singularities of the resolvent, which are associated with
bound states and resonances. The latter are then studied using an appropriate
type of collective coordinates, and a hydrodynamical model of the trapping,
responsible for the resonances, is then proposed. Accordingly, we derive, from
the uncertainty principle, a spin-width of the unstable states which can be
related to their angular lifetime.
