Session GD - Nuclear Structure A<70.
ORAL session, Saturday morning, October 30
Water Tower, Hyatt Regency Chicago
The isoscalar giant dipole resonance(ISGDR) has been measured by single experiments with the use of inelastic \alpha-scattering in many nuclei[1]. However, information on its decay properties is scarce. The decay properties, especially the relative population and total strength of hole states in the (A-1) nucleus resulting from particle decay of giant resonance in nuclei can provide crucial tests for the microscopic model calculations. Caculations based on continuum-RPA approach have recently become abailable and provide results on partial branching ratios for direct neutron and proton decay of ISGDR [2]. We report on a coincidence experiment searching for these direct particle decay branches from the ISGDR in the nucleus ^58Ni. The experiment was performed at the RCNP, Osaka University, using inelastic \alpha-scattering at a beam energy of 400 MeV. The inelastically scattered \alpha particles were detected by the magnetic spectrometer ``Grand Raiden'' at 2.5^\circ, with the decay protons detected by a set of sixteen Si(Li) detectors with a thickness of 5.0 mm and an effective area of 400 mm^2 each placed at backward angles. The result for the observed final states in ^57Co will be presented and compared with the theoretical calculations. References: [1] M.Uchida et al., Phys.Rev. C 69, 051301 (2004), [2] M.L. Gorelik et al., Phys. Rev. C 69, 054322 (2004)