Exotic clusters accessed via resonant scattering

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The concept of the nucleus that is held by many, is of a tightly knit assembly of protons and neutrons, largely spherical and broadly featureless. But just like most things we learn at school the reality is much different. The nucleus is a rather dynamic environment in which the protons and neutrons move in quantized orbits at a sizable fraction of the speed of light. It is these dynamics that are of prime importance when it comes to the determination of the structural properties of the nucleus. Nucleons in the same orbit have large spatial overlaps with each other, and thus interact much more strongly than the mean of the interactions with other nucleons. If two protons and two neutrons (the spins being anti-aligned for identical particles) are in the same orbit, then the spatial overlap of a quartet of particles is maximised, and an alpha-particle emerges from the resulting correlations. In nature, the free alpha-particle, or helium nucleus, is rather robust / it has a very high binding energy / and thus within the confines of the nucleus, under the right conditions, preformed alpha-particles can appear. This in itself is not remarkable, but it is when the nucleus condenses entirely into alpha-particles! For example, certain states in 12C and 16O have been described in terms of a Bose alpha-particle gas. This proposal uses a resonant scattering technique, where alpha-cluster states are formed in collisions between a helium gas and a projectile to examine three classes of states in light nuclei that are predicted to have a truly remarkable structure; (i) Bose-alpha-gas states in 16O and 20Ne, (ii) alpha-particle states in which neutrons are exchanged between the clusters / the nuclear analog of atomic molecules, (iii) three centred cluster structures. All three areas are of key importance in the field of nuclear clustering and have direct links with atomic phenomena.