exotic nuclei structure and reaction noyaux exotiques ... - IPN - IN2P3

keV -ray with the particles and the peak is therefore
ascribed to a transfer to the ground state only.
The two other peaks are know to correspond to
single states. The transferred angular momentum
has been determined for each peak from the comparison
of the extracted angular distribution to distorted
wave Born approximation (DWBA) calculations
performed using the code TWOFNR. Optical
potentials from global formulae were used in the
calculations. Deduced spin and parity are in agreement
with previous studies for the GS and first excited
state. The negative parity of the state at 3.23
MeV is established for the first time.
References:
[1] C. Détraz et al., Phys. Rev. C 19, 169 (1979).
[2] T. Otsuka et al., Phys. Rev. Lett. 95, 232502
(2005).
[3] W.C. Catford et al., J. Phys. G 31, S1655
(2005).
[4] E.C. Pollacco et al., Eur. Phys. J. A 25, 287
(2005).
[5] B.A. Brown, private communication.
[6] M. Stanoiu et al., Phys. Rev. C 17, 034312
(2004).
E(MeV) J E SM J SM
0 (3/2,5/2)+ 0 5/2+
1.408 1/2+ 1.47 1/2+
3.23 (1/2,3/2)- 2.244 1/2-
Table 1 : Comparison of experimental energies
and spin/parities assigned from the
DWBA analysis with shell model calculations
Spectroscopic factors (SF) were further deduced
using the standard procedure of normalization of
the calculated differential cross-section to the data.
Agreement with Shell model calculations is relatively
good taking into account the error on the experimental
SF (25%). The low value of the SF to
the 1/2+ excited state evidences the fact that the
subshell closure at N=14 observed in 22 O [6] is not
yet present in 20 O. In a next step, the comparison
of the present results to existing data on hole
states in 17 O is expected to provide informations on
neutron-neutron components of phenomenological
shell model interactions.
Fig. 2 : Comparison of spectroscopic factors
extracted from the DWBA analysis with shell
model calculations
16