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The fusion cross section for 12C+13C has been measured down to Ec m = 2.6 MeV, at which the cross section is of the order of 20 nb. By comparing the cross sections for the three carbon isotope systems, 12C+12C, 12C+13C, and 13C+13C, it is found that the cross sections for 12C+13C and 13C+13C provide an upper limit for the fusion cross section of 12C+12C over a wide energy range. After calibrating the effective nuclear potential for 12C+12C using the 12C+13C and 13C+13C fusion cross sections, it is found that a coupled-channels calculation with the ingoing wave boundary condition (IWBC) is capable of predicting the major peak cross sections in 12C+12C. A qualitative explanation for this upper limit is provided by the Nogami-Imanishi model and by level density differences among the compound nuclei. It is found that the strong resonance found at 2.14 MeV in 12C+12C exceeds this upper limit by a factor of more than 20. The preliminary result from the most recent measurement shows a much smaller cross section at this energy, which agrees with our predicted upper limit. [ABSTRACT FROM AUTHOR]

The interaction of loosely bound ( Sp = 600 keV) 17F ions with a 208Pb target was studied at Elab = 86 MeV, below the Coulomb barrier, by measuring the differential cross-section for the quasi-elastic scattering and the cross-section for the exclusive breakup process 17F $ \rightarrow$16O + p . The small reaction and exclusive breakup cross-sections confirm the small reactivity of this system, even at low energy, and indicates that the 17F small binding energy plays a minor role in the reaction dynamics. [ABSTRACT FROM AUTHOR]

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,γ)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. Semiclassical 1st-order perturbation theory and fully quantum-mechanical continuum-discretized coupled-channels analyses yield nearly identical results for the E1 strength relevant to solar-neutrino flux calculations, suggesting that theoretical reaction mechanism uncertainties need not limit the precision of Coulomb-breakup determinations of the 7Be( p,γ)8B S-factor. A recommended value of S17(0) based on a weighted average of this and other measurements is presented. This recommendation implies a revised value for the theoretical flux of 8B solar neutrinos, which is also given.-1 [ABSTRACT FROM AUTHOR]

The two-body breakup 17F→16O+p on Ni and Pb targets at 10–40 MeV/u is calculated by solving the time-dependent Schro¨dinger equation numerically. Both Coulomb and the nuclear potentials are important in these reactions, but the Coulomb contribution cannot be calculated reliably in first-order perturbation theory. The most dramatic feature is a dynamic polarization effect, which reduces the Coulomb dissociation probability compared to first-order perturbation theory. Over most of the energy range, the correction is proportional to Z3, the cube of the target charge, and the relative importance is nearly inversely proportional to the beam energy. At the lowest energies in the range considered, higher-order effects (⩾Z3) become significant as well. At the impact parameters where nuclear induced breakup is dominant, the diffraction dissociation is reduced whereas stripping is enhanced compared to the eikonal approximation. Here too the deviations decrease inversely with beam energy over most of the range considered. [Copyright &y& Elsevier]

Energy loss of 2-, 6-, and 15-GeV/c positive and negative protons, kaons, and pions transmitted through thin germanium and silicon crystals are measured using the crystałs as intrinsic detectors. For particles incident in directions far from axial or planar directions the results are in accord with the relativistic Bethé-Bloch stopping theory. The density effect plays an important role at these energies. The spectral distribution of energy losses is in good agreement with the Landau distribution. For positive particles aligned with an axis or a plane, the energy loss is considerably reduced compared to random. The measurements agree well with theoretical calculations. Negative particles, well aligned to a crystal axis, show increased energy loss compared to random by as much as ∼20%., Physics