Collective-coupling analysis of spectra of mass-7 isobars:^{7} He,^{7} Li,^{7} Be, and^{7} B

Physical Review C (Impact Factor: 3.72). 01/2006; 74(6). DOI: 10.1103/PhysRevC.74.064605
Source: arXiv

ABSTRACT A nucleon-nucleus interaction model has been applied to ascertain the underlying character of the negative-parity spectra of four isobars of mass-7, from neutron- to proton-emitter drip lines. With a single nuclear potential defined by a simple coupled-channel model, a multichannel algebraic scattering approach (MCAS) has been used to determine the bound and resonant spectra of the four nuclides, of which 7He and 7B are particle unstable. Incorporation of Pauli blocking into the model enables a description of all known spin-parity states of the mass-7 isobars. We have also obtained spectra of similar quality by using a large space no-core shell model. Additionally, we have studied 7Li and 7Be using a dicluster model. We have found a dicluster-model potential that can reproduce the lowest four states of the two nuclei, as well as the relevant low-energy elastic scattering cross sections. But, with this model, the rest of the energy spectra cannot be obtained.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The structure of 17C is used to define a nuclear interaction that, when used in a multichannel algebraic scattering theory for the n+C16 system, gives a credible definition of the (compound) excitation spectra. When couplings to the low-lying collective excitations of the 16C-core are taken into account, both sub-threshold and resonant states about the n+C16 threshold are found. Adding Coulomb potentials to that nuclear interaction, the method is used for the mirror system of p+Ne16 to specify the low excitation spectrum of the particle unstable 17Na. We compare the results with those of a microscopic cluster model. A spectrum of low excitation resonant states in 17Na is found with some differences to that given by the microscopic cluster model. The calculated resonance half-widths (for proton emission) range from ∼2 to ∼672 keV∼672 keV.
    Nuclear Physics A 04/2012; 879:132–145. · 1.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We describe radiative-capture reactions at low energies within the nuclear coupled-channel approach denoted MCAS (multi-channel algebraic scattering). The amplitude of single-photon emission is constructed via a generalization of the Siegert theorem in an explicit gauge-independent way, without any multipole decomposition of the electromagnetic (e.m.) current operator. As a first test application, we calculate the 3He(α, γ)7Be reaction cross section at astrophysical energies using a simplified two-cluster model. The energy dependence of the calculated astrophysical factor reproduces the experimental situation fairly well, though the cross-section normalization turns out to be overestimated.
    Few-Body Systems 11/2008; 44(1):357-360. · 1.05 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The formalism that describes radiative-capture reactions at low energies within an extended two-cluster potential model is presented. Construction of the operator of single-photon emission is based on a generalisation of the Siegert theorem with which the amplitude of the electromagnetic process is constructed in an explicitly gauge-independent way. While the starting point for this construction is a microscopic (single-nucleon) current model, the resulting operator of low-energy photon emission by a two-cluster system is expressed in terms of macroscopic quantities for the clusters and does not depend directly on their intrinsic coordinates and momenta. The multichannel algebraic scattering (MCAS) approach has been used to construct the initial- and final-state wave functions. We present a general expression for the scattering wave function obtained from the MCAS T matrix taking into account inelastic channels and Coulomb distortion. The developed formalism has been tested on the reaction cross section at astrophysical energies. The energy dependence of the evaluated cross section and S factor agrees well with that extracted from measurement though the calculated quantities slightly overestimate data.
    Nuclear Physics A 06/2008; · 1.53 Impact Factor

Full-text (3 Sources)

Available from
Jun 10, 2014