H. M. Xu

Multifragmentation of toroidal and bubble nuclei within the BUU approach

Abstract Multifragmentation, following the formation of toroidal and bubble nuclei, is observed with an improved Boltzmann-Uehling-Uhlenbeck (BUU) model for central 92 Mo+ 92 Mo collisions. With a stiff equation of state, simultaneous explosion into several nearly-equal fragments (NEFs) in a ring-like manner occurs due to the formation of metastable toroidal nuclei. In contrast, with a soft equation of state, simultaneous explosion into several NEFs in a volume-like manner occurs due to the formation of metastable bubble nuclei. Guided by our BUU model, we propose two signatures: (1) because of the geometries of bubbles and toroids and because of the cold breakup at low temperatures, we predict enhanced cross sections for NEFs at small center-of-mass energies. (2) the coplanarity of these NEFs could carry important information concerning the geometry of the sources. This, in turn, could provide information about the stiffness of the equation of state. Finally, the dependence of these two predictions on the number of test particles, impact parameters, and the initial random seeds are assessed.

Asymptotic normalization coefficients and astrophysical radiative capture reactions

Abstract The differential cross sections for the reactions 9 Be( 10 B, 9 Be) 10 B at an incident 10B energy of 100 MeV and 16 O( 3 He,d) 17 F ∗ (0.495 MeV , 1 2 + ) at an incident 3He energy of 29.75 MeV were measured. By normalizing the theoretical DWBA proton exchange cross sections to the experimental ones, the asymptotic normalization coefficients (ANCs) for the virtual decays 10 B → 9 Be+p and 17 F ∗ (0.495 MeV ) → 16 O+p have been found. These ANCs are used to calculate the S(0)-factors for the direct radiative captures 9 Be + p → 10 B + γ and 16 O + p → 17 F ∗ (0.495 MeV ) + γ .

Asymptotic normalization coefficients for 14N→13C+p and 10B→9Be+p

The proton exchange reactions {sup 13}C({sup 14}N,{sup 13}C){sup 14}N and {sup 9}Be({sup 10}B,{sup 9}Be){sup 10}B were studied at energies where they are peripheral. Angular distributions for elastic scattering and proton transfer were measured, and the results were used to extract ANCs by comparison with modified DWBA calculations. These ANCs will be used together with proton transfer reactions with radioactive beams to determine astrophysical S-factors for radiative capture reactions, in particular S{sub 17}(0) for {sup 7}Be(p,{gamma})The proton exchange reactions 13C(14N,13C)14N and 9Be(10B,9Be)10B were studied at energies where they are peripheral. Angular distributions for elastic scattering and proton transfer were measured, and the results were used to extract ANC’s by comparison with modified DWBA calculations. These ANC’s will be used together with proton transfer reactions with radioactive beams to determine astrophysical S-factors for radiative capture reactions, in particular S17(0) for 7Be(p,γ).