The Photodissociation of 8B^8B and the Solar Neutrino Problem

The extraction of the photodissociation cross sections of $^8B$ from Coulomb dissociation experiments is investigated. A careful study is done on the contributions of the E1, E2 and M1 multipolarities to the breakup. A comparison with the data of a recent experiment is performed. It is shown that the extraction of the radiative capture cross sections $^7Be(p,\ \gamma)^8B$ which are relevant for the solar neutrino problem is not affected appreciably by Coulomb reacceleration. A non-perturbative model is used for the purpose. Emphasis is put on the perspectives for future experiments which are planned at the University of Notre Dame, RIKEN (Japan), and GSI (Germany). An analysis of the total yields of ``photon-point" processes in inelastic electron scattering is also done.Comment: 23 pages, plain Latex. 12 figures available upon request

Nuclear Astrophysics in Storage Rings

Nuclear reaction cross sections are usually very small in typical astrophysical environments. It has been one of the major challenges of experimental nuclear astrophysics to assess the magnitude of these cross sections in the laboratory. For a successful experiment high luminosity beams are needed. Increasing the target width, one also increases the reaction yields. But, this is of limited use due to multiple scattering in the target. Storage rings are a very good way to overcome these difficulties. In principle, they can be tuned to large luminosities, and have the advantage of crossing the interaction region many times per second (typically one million/s), compensating low density internal gas targets, or low reaction rates in beam-beam collisions. Storage rings are also ideal tools for precise measurements of masses and beta-decay lifetimes of nuclei of relevance for astrophysics.Comment: 14 pages, LaTeX, figures available upon reques

Clustering in stable and unstable nuclei in pp-shell and sdsd-shell regions

According to microscopic calculations with antisymmetrized molecular dynamics, we studied cluster features in stable and unstable nuclei. A variety of structure was found in stable and unstable nuclei in the $p$-shell and $sd$-shell regions. The structure of excited states of $^{12}$Be was investigated, while in $sd$-shell nuclei we focused on molecular states and deformed states. The deformed states in $^{28}$Si and $^{40}$Ca were discussed in connection with the high-lying molecular states. Appealing molecular states in $^{36}$Ar and $^{24}$Mg were suggested. The results signified that both clustering of nucleons and mean-field formation are essential features in $sd$-shell nuclei as well as $p$-shell nuclei.Comment: 5 pages, 2 figs, proceedings of the 8th International conference on Clustering Aspects of Nuclear Structure and Dynamics, Nov. 2003, Nara, Japan, to be published in Nucl.Phys.

Breakup of the weakly bound 17F nucleus

The breakup of the radioactive 17F nucleus into a proton and 16O is studied for the reaction 17F + 208Pb --> p + 16O + 208Pb at 65 MeV/nucleon. The possibility of using this reaction as a test case for studying dynamical Coulomb reacceleration effects is assessed. It is shown that the reaction is dominated by elastic nuclear breakup (diffraction dissociation).Comment: 17 figures and 8 figure

Kinetic energy and spin-orbit splitting in nuclei near neutron drip line

Two important ingredients of nuclear shell-structure, kinetic energy and spin-orbit splitting, are studied as a function of orbital angular momenta \ell and binding energies, when binding energies of neutrons decrease towards zero. If we use the standard parameters of the Woods-Saxon potential in \beta stable nuclei and approach the limit of zero binding energy from 10 MeV, the spin-orbit splitting for n=1 orbitals decreases considerably for \ell=1, while for \ell > 2 little decreasing is observed in the limit. In contrast, the kinetic energy decreases considerably for \ell \simleq 3. The smaller the \ell values of orbitals, the larger the decreasing rate of both kinetic energy and spin-orbit splitting. The dependence of the above bservation on the diffuseness of potentials is studied.Comment: 12 pages, 3 figures, submitted to Nucl. Phy

On the Analysis of Intermediate-Energy Coulomb Excitation Experiments

In a recent publication (Bertulani et al., PLB 650 (2007) 233 and arXiv:0704.0060v2) the validity of analysis methods used for intermediate-energy Coulomb excitation experiments was called into question. Applying a refined theory large corrections of results in the literature seemed needed. We show that this is not the case and that the large deviations observed are due to the use of the wrong experimental parameters. We furthermore show that an approximate expression derived by Bertulani et al. is in fact equivalent to the theory of Winther and Alder (NPA 319 (1979) 518), an analysis method often used in the literature.Comment: 10 pages, 1 figure, submitted to PL

Interfacial Structure at the Quaternary Ammonium-Based Ionic Liquids vertical bar Gold Electrode Interface Probed by Surface-Enhanced Infrared Absorption Spectroscopy: Anion Dependence of the Cationic Behavior

The interfacial structure at the quaternary ammonium-based ionic liquids(ILs)|gold(Au) electrode interface has been studied using surface-enhanced infrared absorption spectroscopy (SEIRAS). Four anions, bis(perfluoroalkanesulfonyl)amide (CₙCₙN⁻; n = 0, 1, 2, 4), have been combined with a quaternary ammonium cation, trioctylmethylammonium (N₈₈₈₁⁺), to investigate the influence of the perfluoroalkyl chain length of the anion on the behavior of the quaternary ammonium cation at the interface. In addition, to investigate the effect of the alkyl chain length of the quaternary ammonium cations on the cationic behavior, we have also combined a cation with a shorter alkyl chain, tributylmethylammonium (N₄₄₄₁⁺) with C₁C₁N⁻. Thus, we have performed SEIRAS measurements at the Au interface of five ILs: [N₈₈₈₁⁺][CₙCₙN⁻] (n = 0, 1, 2, 4) and [N₄₄₄₁⁺][C₁C₁N⁻]. The four CH stretching bands originating from the quaternary ammonium cations have been individually analyzed, enabling us to reveal the behavior of the quaternary ammonium cations at the interface. The cationic behavior is found to dramatically depend not only on the alkyl chain length but also on the perfluoroalkyl chain length of the counterion. For [N₈₈₈₁⁺][C₄C₄N⁻] and [N₈₈₈₁⁺][C₂C₂N⁻], octyl chains of N₈₈₈₁⁺cannot reach the Au electrode surface at positive potentials because the bulky anions in the first ionic layer on the electrode surface block the approach. Conversely, for ILs with the smaller anions ([N₈₈₈₁⁺][C₁C₁N⁻] and [N₈₈₈₁⁺][C₀C₀N⁻]), octyl chains of N₈₈₈₁⁺ can penetrate into a space in the first ionic layer of small anions. The butyl chains of N₄₄₄₁⁺ in [N₄₄₄₁⁺][C₁C₁N⁻] cannot reach the surface at positive potentials even across the first ionic layer of the small anions because of their relatively short alkyl chain length

Collective Properties of Low-lying Octupole Excitations in 82208Pb126^{208}_{82}Pb_{126}, 2060Ca40^{60}_{20}Ca_{40} and 828O20^{28}_{8}O_{20}

The octupole strengths of $\beta$-stable nucleus $^{208}_{82}Pb_{126}$, a neutron skin nucleus $^{60}_{20}Ca_{40}$ and a neutron drip line nucleus $^{28}_{8}O_{20}$ are studied by using the self-consistent Hartree-Fock calculation plus the random phase approximation (RPA) with Skyrme interaction. The collective properties of low-lying excitations are analyzed by using particle-vibration coupling. The results show that the lowest isoscalar states above threshold in $^{60}_{20}Ca_{40}$ and $^{28}_{8}O_{20}$ are the superpositions of collective excitations and unperturbed transitions from bound state to nonresonance states. For these three nuclei, both the low-lying isoscalar states and giant isoscalar resonance carry isovector strength. The ratio B(IV)/B(IS) is checked. It is found that, for $^{208}_{82}Pb_{126}$, the ratios are equal to $(\frac{N-Z}{A})^2$ in good accuracy, while for $^{60}_{20}Ca_{40}$ and $^{28}_{8}O_{20}$, the ratios are much larger than $(\frac{N-Z}{A})^2$. This results from the excess neutrons with small binding energies in $^{60}_{20}Ca_{40}$ and $^{28}_{8}O_{20}$.Comment: 14 pages, 10 figure