Electromagnetic dissociation as a tool for nuclear structure and astrophysics

Abstract

Coulomb dissociation is an especially simple and important reaction mechanism. Since the perturbation due to the electric field of the (target) nucleus is exactly known, firm conclusions can be drawn from such measurements. Electromagnetic matrixelements and astrophysical S-factors for radiative capture processes can be extracted from experiments. We describe the basic elements of the theory of nonrelativistic and relativistic electromagnetic excitation with heavy ions. This is contrasted to electromagnetic excitation with leptons (electrons), with their small electric charge and the absence of strong interactions. We discuss various approaches to the study of higher order electromagnetic effects and how these effects depend on the basic parameters of the experiment. The dissociation of neutron halo nuclei is studied in a zero range model using analytical methods. We also review ways how to treat nuclear interactions, show their characteristics and how to avoid them (as far as possible). We review the experimental results from a theoretical point of view. Of special interest for nuclear structure physics is the appearence of low lying electric dipole strength in neutron rich nuclei. Applications of Coulomb dissociation to some selected radiative capture reactions relevant for nuclear astrophysics are discussed. The Coulomb dissociation of 8 B is relevant for the solar neutrino problem. The potential of the method especially for future investigations of (medium) heavy exotic nuclei for nuclear structure and astrophysics is explored. We conclude that the Coulomb dissociation mechanism is theoretically well understood, the potential difficulties are identified and can be taken care of. Many interesting experiments have been done in this field and many more are expected in the future.

A realistic solvable model for the Coulomb dissociation of neutron halo nuclei

“…3. For small values of q coul the two terms almost cancel and the expansion in q coul was found to be in agreement with the semiclassical result, see [13] and below.…”

“…On the other hand the 1 st order semiclassical Coulomb excitation theory was widely applied in the past years to the Coulomb dissociation of high energy neutron halo nuclei, see, e.g., [13]. The theory corresponds to the "prior form", mentioned above.…”

“…The absolute square of a(b) gives the breakup probability P (b), in lowest order (LO). It is given by [13,14] …”

Determining the7Li(n,γ) cross section via Coulomb dissociation of8Li

“…In nuclear astrophysics, neutron capture cross sections (σ n,γ ) on radioactive nuclei are important in nucleogenesis, and a cross-section measurement of the inverse reaction, Coulomb dissociation [3,4], might be the only way to obtain the capture cross sections. Complementary indirect techniques to determine neutron-capture cross sections, such as so-called "surrogate" methods, have been utilized in other systems, but comparison to Coulomb dissociation as well as direct measurements is desirable to better understand the applicability of such approaches [5].…”

The s-process nucleosynthesis in massive stars: current status and uncertainties due to convective overshooting

“…Reeves, 1994;Vangioni-Flamet al, 2000), the experimental techniques and theoretical methods used to investigate nuclear processes of astrophysical interest (e.g. Angulo, 2009;Baur et al, 2003;Bertulani & Gade, 2010;Costantini, 2009;Spitaleri, 2010;Thielemann et al, 2001;Typel & Baur, 2003). (for details see e.g.…”