Clusters and covalently bound nuclear molecules

Nuclear clustering based on α particles and strongly bound substructures with N = Z has been studied. Of particular interest are excited states close to the decay thresholds into substructures, as described by the Ikeda-diagram. This diagram can be extended to neutron-rich nuclei, in these cases strongly deformed isomeric states consisting of clusters and loosely bound neutrons will appear. A possible approach to describe these states is to use explicitly molecular concepts, with neutrons in covalent binding orbits. Examples for molecular structure in beryllium isotopes and in other neutron-rich light nuclei (carbon and neon ) are discussed