Nuclear structure and reaction studies at SPIRAL

The SPIRAL facility at GANIL, operational since 2001, is described briefly. The diverse physics program using the re-accelerated (1.2 to 25 MeV/u) beams ranging from He to Kr and the instrumentation specially developed for their exploitation are presented. Results of these studies, using both direct and compound processes, addressing various questions related to the existence of exotic states of nuclear matter, evolution of new "magic numbers", tunnelling of exotic nuclei, neutron correlations, exotic pathways in astrophysical sites and characterization of the continuum are discussed. The future prospects for the facility and the path towards SPIRAL2, a next generation ISOL facility, are also briefly presented.Comment: 48 pages, 27 figures. Accepted for publication in Journal of Physics

High-spin spectrum of 24Mg studied through multiparticle angular correlations

We describe the investigation of high-spin states in 24Mg populated with the 12C(16O,α)24Mg reaction at 62- and 68-MeV beam energy. The excited states were established through the coincident detection of up to four α and γ particles in complete decay cascades toward a final state of angular momentum zero, the ground state of either 20Ne or 16O. We describe a new analysis method for the angular correlations in such events and apply it with the goal to assign spin and parity to α-unbound states in 24Mg. We establish a number of high-spin, natural-parity states between spins 6 and 12, including the lowest known 10+ and 12 + levels. The energy systematics of positive- and negative-parity high-spin states are compared to the predictions of modern shell-model calculations

γ-ray spectroscopy of one-proton knockout from 45Cl

The role of proton shell effects in the structure of the N=28 isotones 45Cl and 44S has been studied via one-proton knockout from 45Cl. We compare measured γ-ray intensities, inclusive and partial knockout cross sections, and the inclusive momentum distribution of outgoing 44S particles with shell-model and reaction-theory predictions. The strong population in this reaction of the recently identified 41+ state in 44S, identified through its subsequent γ-ray decay energy, makes a compelling case for a Jπ=3/2+ ground state in 45Cl