The Loosely Bound Proton in 13 N and the Transfer Reaction 11 B (13 N, 12 C) 12 C
Date
1997Author
Neal, Richard J
Metadata
Abstract
The radioactive nucleus 13 N (t 1/2 = 10 min, J ß = 1/2) contains one loosely
bound proton (Sp = 1.94 MeV) which can be considered to be bound to a
core of 12 C. Taking advantage of the recent availability of beams of radioactive nuclei at Louvain-la-Neuve, Belgium, a beam of 13 N has been used to in
vestigate the transfer reaction 11 B( 13 N, 12 C) 12 C. Particle-γ coincidence data was
taken, using the LEDA silicon strip array and BaF2 modules, gating on the
15.11 MeV γ-decay from the T = 1 state in 12 C*. Two final states, corresponding
to 12C gs + 12C* (15.11 MeV) and 12 C* (4.44 MeV)+ 12C* (15.11 MeV) have been observed and angular distributions have been measured for both transitions at each
of two beam energies, 29.5 MeV and 45 MeV.
The results are discussed with special reference to the loosely bound nature of the
valence proton in 13 N; the transfer reaction has been modelled using a DWBA
code, with the 13N ground state constructed as a mixture of states: a p 1/2 proton bound to 12C gs , or a p 3/2 proton bound to 12 C*
2+ (4.44 MeV). Fits to the
experimental data have been obtained using a very shallow set of optical poten
tials, which are found to be energy dependent. The agreement with experiment
is good, with the exception of the 12C* (4.44)+ 12 C*(15.11) transition at the lower
beam energy, which is significantly underestimated by the calculations, suggest
ing a contribution from a different reaction mechanism.