Münster 2002 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 39: Nuclear Physics / Spectroscopy VI

HK 39.1: Group Report

Thursday, March 14, 2002, 14:00–14:30, B

Neutron decay studies of the Isoscalar Giant Dipole Resonance — •M. Hunyadi¹, A.M. van den Berg¹, N. Blasi², B. Davids¹, U. Garg³, J. Gulyás⁴, M.N. Harakeh¹, M.A. de Huu¹, D. Sohler⁴, and H.J. Wörtche¹ — ¹Kernfysisch Versneller Instituut, Groningen, The Netherlands — ²INFN Milano, Milano, Italy — ³University of Notre Dame, Notre Dame, USA — ⁴Institute of Nuclear Research, Debrecen, Hungary

The Isoscalar Giant Dipole Resonance (ISGDR) is the response of the nucleus to the second-order isoscalar dipole operator. motion). Its energy systematics are important in the determination of the nuclear incompressibility. So far, only singles experiments, using inelastic α-scattering, gave evidence for the ISGDR in a few nuclei, but they suffered from strong instrumental and nuclear-continuum backgrounds at very forward angles, and a partial overlap with the isoscalar giant octupole resonance. Presently, no experimental data are available on the decay properties of the ISGDR, which would be a crucial test for the theoretical descriptions of its microscopic structure and damping process.

Recently we performed coincidence experiments using inelastic α- scattering at 50 MeV/A searching for the direct neutron decay of the ISGDR in ²⁰⁸Pb, ¹²⁴Sn and ⁹⁰Zr. A clear indication of the presence of the direct decay component was obtained. Moreover, we exploited the advantage of the coincidence technique resulting in a considerable suppression of the background contribution. These results enabled the direct comparison with a recently published CRPA calculation.