Coplanar ternary decay of hyper-deformed $^{56}$Ni
Résumé
Ternary fission events from the decay of $^{56}$Ni compound nuclei, formed in the $^{32}$S + $^{24}$Mg reaction at $E_{lab}(^{32}S)$ = 163.5 MeV, have been measured in a unique set-up consisting of two large area position sensitive (x,y) gas detector telescopes. Very narrow out-of-plane correlations are observed for two fragments emitted in either purely binary events or in events with a missing mass consisting of 2 and 3 $\alpha$-particles. These correlations are interpreted as ternary fission decay from compound nuclei at high angular momenta through an elongated (hyper-deformed) shape with very large moments of inertia, where the lighter mass in the neck region remains at rest.