GIANT DIPOLE RADIATION AND ISOSPIN MIXING IN HOT LIGHT NUCLEI

摘要

Probability of isospin mixing at high excitation has been determined only for few nuclei. Thus, we attempted to extract the degree of isospin mixing in several light, self-conjugate compound nuclei at excitation energy around 50 MeV and study its dependence on atomic mass number. For this purpose we have studied the statistical decay of the Giant Dipole Resonance (GDR) built on excited states formed in heavy-ion fusion reactions. We have measured the ~(20)Ne + ~(12)C, ~(12)C + ~(24)Mg, ~(20)Ne + ~(24)Mg and ~(36)Ar + ~(24)Mg reactions populating N = Z compound nuclei: ~(32)S, ~(36)Ar, ~(44)Ti, ~(60)Zn and the ~(19)F + ~(12)C, ~(12)C + ~(25)Mg, ~(20)Ne + ~(25)Mg and ~(36)Ar + ~(25)Mg reactions populating neighbouring compound nuclei with N ? Z at close excitation energy (temperature). Heavy-ion beams from the Warsaw Cyclotron have been used. High-energy γ-rays emitted in the reactions have been measured with the JANOSIK set-up. Measured spectra have been fitted with the CASCADE statistical model calculations assuming a Lorentzian GDR strength function.