First evidence for the hyperdeformed nuclear shape at high angular momentum

A ridge structure consisting of stretched E2 transitions and extending from ħω≃0.6 to 0.75 MeV has been found in a proton-selected γ-γ matrix in the reaction Sn120(37Cl, xn)152,153Dy at 187 MeV. The ridge spacing corresponds to a dynamic moment of inertia, scrI(2), of about 130ħ2 MeV-1 and suggests the existence of a hyperdeformed prolate shape with a quadrupole deformation β2≥0.9. Furthermore, a cascade of 10 discrete transitions with an average energy spacing of 30±3 keV has been found. This result is consistent with calculations indicating conditions favorable to hyperdeformed structures.