S17(0) Determined from the Coulomb Breakup of 83 MeV/nucleon 8B

A kinematically complete measurement was made of the Coulomb dissociation of 8B nuclei on a Pb target at 83 MeV/nucleon. The cross section was measured at low relative energies in order to infer the astrophysical S factor for the 7Be(p,gamma)8B reaction. A first-order perturbation theory analysis of the reaction dynamics including E1, E2, and M1 transitions was employed to extract the E1 strength relevant to neutrino-producing reactions in the solar interior. By fitting the measured cross section from Erel = 130 keV to 400 keV, we find S17(0) = 17.8 (+1.4, -1.2) eV b

New evidence for a subshell gap at N = 32

Abstract An 879.9(2) keV γ -ray transition has been identified following the β decay of 58 V and assigned as the 2 58 Cr 34 . A peak in the energies of the first excited 2 + states for the even-even chromium isotopes is now evident at 56 Cr 32 , providing empirical evidence for a significant subshell gap at N = 32. The appearance of this neutron subshell closure for neutron-rich nuclides may be attributed to the diminished π1f 7/2 -ν1f 5/2 monopole proton-neutron interaction as protons are removed from the 1f 7/2 single-particle orbital. 2001 Elsevier Science B.V. All rights reserved. PACS: 21.60.Cs; 23.20.Lv; 27.40.+z Trends in nuclear masses and binding energies have suggested nuclei associated with nucleon numbers expected to be maximum at midshell. However, the development of collectivity away from major closed shells may be inhibited by the presence of subshell closures, or minor shell gaps. In order to study such phenomena, experimental probes of quadrupole collectivity may be utilized. One measure of the extent of quadrupole collectivity in even-even nuclear systems is the energy of the first excited 2 + state, E(2 + 1 ). According to Grodzins [2