J.A. Behr

Search for a phase transition in the nuclear shape at finite temperature and rapid rotation

Abstract At high spin the strength function for γ-decay of the Giant Dipole Resonance in highly excited 45 Sc compound nuclei exhibits a shoulder at E γ ≈ 25 MeV, in addition to the main peak at E γ ≈ 16 MeV, suggesting the presence of large deformations β > 0.45. Calculated spectral shapes including thermal shape fluctuations provide a good description of the data when the nuclear potential energy surface includes the oblate → triaxial phase transition predicted by the rotating liquid drop model at high spin.

Systematic behaviour of the giant dipole resonance in highly excited nuclei

A study of the statistical decay of the giant dipole resonance (GDR) built on excited nuclear states provides information on nuclear properties at finite temperature and moderate spin. The results of a systematic investigation of GDR properties at high excitation covering a wide mass range, A approximately 40-170 are presented. The observed resonance strengths and mean resonance energies vary smoothly as a function of mass and are in agreement with the properties of the ground-state GDR. The widths and resonance shapes of the GDR in highly excited nuclei reflect the deformation of the nucleus at finite temperature and spin.

Shape changes and isospin purity in highly excited light mass nuclei

The statistical decay of the Giant Dipole Resonance built on a highly excited states of light-mass nuclei was studied in inclusive experiments. Results of the search for a shape change of hot, fast-rotating {sup 45}Sc and the test of the isospin purity at high excitation in {sup 28}Si and {sup 26}Al are reported.