Giant resonance decays in 20Ne, 22Ne and interference effects with quasifree scattering processes

Abstract

The charged particle (c) decay from excited states up to the giant quadrupole resonance (GQR) in 20Ne has been studied in a kinematically complete 20Ne(α, α′ c) coincident experiment at E α = 155 MeV. Angular correlation functions and branching ratios are extracted for the α 0, α 1 and p 0 decay channels. The ( α, α′ α 0) angular correlation functions are analysed in PWBA in terms of coherent interference with the quasifree scattering process leading to the same final states. Good fits to the data are achieved over a large range of excitation energies. Branching ratios have been extracted and compared to results of Hauser-Feshbach calculations. Above E x = 12.5 MeV excitation energy a discrepancy was found between the experimentally observed α 0 branching ratios and the HF predictions. These results yield evidence for a direct α 0 decay mechanism of the split isoscalar giant quadrupole resonance in 20Ne. Some results are presented also for a 22Ne(α, α′ c) coincidence experiment. Qualitative comparison has been made between the general decay behaviour of the two Ne isotopes.