Extreme nuclear shapes examined via giant dipole resonance lineshapes in hot light-mass systems

The influence of α clustering on nuclear reaction dynamics is investigated using the giant dipole resonance (GDR) lineshape studies in the reactions 20Ne (Elab=145,160 MeV) + 12C and 20Ne (Elab=160 MeV) + 27Al, populating 32S and 47V, respectively. The GDR lineshapes from the two systems are remarkably different from each other. Whereas, the non-α-like 47V undergoes Jacobi shape transition and matches exceptionally well with the theoretical GDR lineshape estimated under the framework rotating liquid drop model (RLDM) and thermal shape fluctuation model (TSFM) signifying shape equilibration, for the α cluster 32S an extended prolate kind of shape is observed. This unusual deformation, seen directly via γ decay for the first time, is predicted to be due to the formation of orbiting dinuclear configuration or molecular structure of 16O + 16O in the 32S superdeformed band.