Competition between quasi-molecular resonances and fusion-fission in light dinuclear systems

Abstract

The results presented in this paper clearly suggest that a coherent framework may exist which connects the topics of heavy-ion molecular resonances, hyperdeformation effects, and fission shape isomerism. New data on particle-particle-$\gamma$ triple coincidences of the $^{28}$Si+$^{28}$Si reaction at a beam energy corresponding to the population of a conjectured J$^{\pi}$ = 38$^{+}$ resonance in $^{56}$Ni are presented. The absence of alignment of the spins of the outgoing fragments with respect to the orbital angular momentum is found to be in contrast with the alignment as measured for the $^{24}$Mg+$^{24}$Mg resonances. A molecular-model picture is presented to suggest a "butterfly" motion of two oblate $^{28}$Si nuclei interacting in a equator-to-equator molecular configuration.Comment: 10 pages standard REVTeX file, 7 ps and eps Figures included -- Talk given at the International Conference ``Nuclear Physics close to the Barrier", Warsaw, Poland, June 30- July 4, 1998 (Proceedings to be published in Acta Physica Polonica A, fall 1998) -