Gamow Shell Model Description of Weakly Bound Nuclei and Unbound Nuclear States

We present the study of weakly bound, neutron-rich nuclei using the nuclear shell model employing the complex Berggren ensemble representing the bound single-particle states, unbound Gamow states, and the non-resonant continuum. In the proposed Gamow Shell Model, the Hamiltonian consists of a one-body finite depth (Woods-Saxon) potential and a residual two-body interaction. We discuss the basic ingredients of the Gamow Shell Model. The formalism is illustrated by calculations involving {\it several} valence neutrons outside the double-magic core: $^{6-10}$He and $^{18-22}$O.Comment: 19 pages, 20 encapsulated PostScript figure

An above-barrier narrow resonance in ¹⁵F

Intense and purified radioactive beam of post-accelerated $^{14}$O was used to study the low-lying states in the unbound $^{15}$F nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at E$\_R$=4.757(6)(10)~MeV with a width of $\Gamma$=36(5)(14)~keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a $^{12}$C core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the $2s\_{1/2}$ shell.Comment: 8 pages, 2 figures, 1 table, Submitted to Phys. Lett.

Real- and Complex-Energy Non-conserving Particle Number Pairing Solution

Many-body open quantum systems are characterized by the correlations between bound and scattering states. In contrast to a closed system (i.e., a very well bound many-body system), the continuous part of the energy spectrum has to be considered explicitly due to the proximity of the Fermi level to the continuums threshold. In this work we show how to introduce these correlations through the continuum single-particle level density (CSPLD) in the pairing framework. By isolating the resonances of the system using an analytic continuation, we arrive at the Berggren (complex-energy) representation of the pairing solutionFil: Id Betan, Rodolfo Mohamed. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Study of the threshold anomaly in the elastic scattering of d+ 197Au

Measurements of the elastic scattering angular distribution for the d+ 197Au system were carried out covering deuteron incident energies in the range from 5 to 16 MeV, i.e. approximately 50% below and above the Coulomb barrier. A critical interaction distance of d I = 2.49 fm was determined from these distributions, which is comparable to that of the radioactive halo nucleus 6He. The experimental angular distributions were systematically analyzed using two alternative models: the semi-microscopic São Paulo and the effective Woods-Saxon optical potentials, for which the best-fitting parameters were determined. These potentials, integrated with the vicinity of the sensitivity radius, were calculated for each energy. For both models, the energy dependence of these integrals presented the breakup threshold anomaly around the coulomb barrier, a typical signature of weakly bound nuclei.Fil: Giudice, T. Comisión Nacional de Energía Atómica; ArgentinaFil: Abriola, D.. Comisión Nacional de Energía Atómica; ArgentinaFil: Arazi, Andres. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Barbará, E.. Comisión Nacional de Energía Atómica; ArgentinaFil: Cardona, Maria Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Gómez, J.. No especifíca;Fil: Hojman, Daniel Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Id Betan, Rodolfo Mohamed. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Kohen, M.S.. Comisión Nacional de Energía Atómica; ArgentinaFil: Llaneza, N.. Universidad Nacional de Rosario; ArgentinaFil: Martí, G.V .. Comisión Nacional de Energía Atómica; ArgentinaFil: Da Fonseca Paes Ribeiro, Barbara Esther. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Schneider, David Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Soler de Oliveira, Hugo. Universidade Federal Fluminense; BrasilFil: Lubian, J.. Universidade Federal Fluminense; Brasi