A Croatian physicist who founded and directed in 1972 the Laboratory for Nuclear Spectroscopy (later renamed to Laboratory for Heavy-Ion Physics) of the Ruđer Bošković Institute Nikola Cindro was concentrated on heavy-ion reactions. The first success in the field was the discovery of the fragmentation of `gross resonances' in the 12C + 12C reaction, followed by the development of a model that explained it in terms of the rotation-vibration coupling in the composite nucleus.
He studied heavy-ion resonances in several laboratories: CEN Saclay, CE Bruyères-le-Châtel, Los Alamos NL, INP Demokritos, CRN/IReS Strasbourg, LN Legnaro and LNS Catania. About the same time Nikola Cindro developed the so-called orbiting cluster model, based on the 'molecular window' concept of W. Scheid and W. Greiner.
This phenomenological model which predicts the occurrence or absence of resonances in a given nuclear system and the general trend of their gross structure has very successfully served as the guide to experimental investigations during the last two decades (cf. U. Abbondanno, Phys. Rev. C 43 (1991) 1484, The persistent success of the orbiting-cluster model). In collaboration with W. Greiner he predicted hyperdeformation in nuclei . He established a group of active collaborators in Zagreb often dubbed the Zagreb school of heavy-ion physics.