2+ States of 8Be

Abstract

Analysis by many-level R-matrix theory of the d-wave "'-'" scattering phase shift suggests the existence of broad 2+ excited states of 8Be, but their properties depend sensitively on the assumed channel radius a2. A simultaneous fit to the 9Be(p, d)8Be deuteron spectrum near the 2, 9 MeV peak requires a2 "'" 7·1 fm, while a simultaneous fit to the ",-particle spectra following 8Li and 8B p-decays requires a2 "'" 6· 7 fm. For the best overall fit with a2 = 6·75 fm, the first 2+ excited state is at 2· 84 MeV excitation energy with a width at half maximum of 1·30 MeV. It is shown that data from other reactions which appeared to give much larger widths for this level can be fitted using the same R-matrix parameters. A second 2+ excited state is obtained at about 9 MeV with a width of about 10 MeV. Properties of the narrow 2+ states at 16·6 and 16·9 MeV are also discussed.