Three-body final states in O16+C12-induced reactions: The structure of Mg24 at high excitation

A kinematically complete study has been made of the C12+O16→C12+C12+α and C12+O16→Ne20+ reactions at E16O=58.3 MeV (lab). α particles were detected at a mean laboratory angle of 2°, while the remaining reaction products were observed in coincidence by two large-area position-sensitive detectors placed symmetrically about the beam axis and subtending angles in the range 15≤θlab≤75. Particle identification was based on the reaction kinematics. Intense yields to the lowest four states of Ne20 were observed, with a significant fraction thereof proceeding through well defined intermediate states in Mg24. The predominant interaction in the C12+C12+α final state appears to involve C12+α corresponding to an excited state at O16 near 10 MeV excitation. No evidence was found for a C12+C12 final state interaction, i.e., for quasimolecular states in Mg24 in the region of excitation 21≤E*≤29 MeV. The predictions of a Hauser-Feshbach statistical model agree rather well with the observed Ne20+α+α yields. A selected portion of the C12+C12+α yield, not necessarily proceeding through an excited state in O16, is accounted for by a statistical model assuming formation and decay of compound states in Mg24. [NUCLEAR REACTIONS C12(O16,α0α1)Ne20, C12(O16,α0C112)C212, E=58.3 MeV; measured σ(Eα0,1,E20Ne;θα1,θ20Ne), σ(Eα0,E12C1,2;θ12C1,2), θα0=2. Deduced intermediate α-C12 interaction; Hauser-Feshbach analysis. Position-sensitive detectors.]