Unbound exotic nuclei studied by projectile fragmentation

Abstract

We call projectile fragmentation of neutron halo nuclei the elastic breakup (diffraction) reaction, when the observable studied is the neutron-core relative energy spectrum. This observable has been measured in relation to the Coulomb breakup on heavy target and recently also on light targets. Such data enlighten the effect of the neutron final state interaction with the core of origin. Projectile fragmentation is studied here by a time dependent model for the excitation of a nucleon from a bound state to a continuum resonant state in a neutron-core complex potential which acts as a final state interaction. The final state is described by an optical model S-matrix so that both resonant and non resonant states of any continuum energy can be studied as well as deeply bound initial states. It turns out that due to the coupling between the initial and final states, the neutron-core free particle phase shifts are modified, in the exit channel, by an additional phase. Some typical numerical calculations for the relevant observables are presented and compared to experimental data. It is suggest that the excitation energy spectra of an unbound nucleus might reflect the structure of the parent nucleus from whose fragmentation they are obtained.

Halo nuclei, stepping stones across the drip-lines

“…The data analysis presented in [52,85,86] shows that similar structures are observed, while the interpretations differ [73]. Good progress was made, with the data [85] of Kondo et al providing a gamma coincidence measurement, thus allowing to obtain better access to core-excited states.…”

“…A compatible result is obtained in a more recent experiment [72] at MSU displayed in figure 12. Here another seed nucleus 14 B with a different ground-state configuration [73] is used. In this case, neutrons are expected to be found in the (0d 5/2 ) 1 and (1s 1/2 ) 1 orbitals with about 30 and 66% probability, respectively.…”

“…In order to study the seed nucleus 14 Be, its subsystem 13 Be, has been studied [52,73] extensively. Its core, 12 Be is expected [76][77][78] to be easily polarizable.…”

Physics with low energy radioactive beams

“…The coordinate system and other details of the calculations can be found in Ref. [22]. The probability spectrum reads…”

Unbound Exotic Nuclei Studied by Projectile Fragmentation

“…The coordinate system and other details of the calculations can be found in Ref. [ 12]. In the special case of exotic nuclei the traditional approach to inelastic excitations needs to be modified.…”