Decay pattern of pygmy states observed in neutron-rich 26Ne.
Coulomb excitation of the exotic neutron-rich nucleus (26)Ne on a (208)Pb target was measured at 58 MeV/u in order to search for low-lying E1 strength above the neutron emission threshold. This radioactive beam experiment was carried out at the RIKEN Accelerator Research Facility. Using the invariant mass method in the 25Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV excitation energy. By performing a multipole decomposition of the differential cross section, a reduced dipole transition probability of B(E1)=0.49+/-0.16e(2) fm(2) is deduced, corresponding to 4.9+/-1.6% of the Thomas-Reiche-Kuhn sum rule. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is measured. The extracted decay pattern is not consistent with several mean-field theory descriptions of the pygmy states.
Gibelin
J
J
Institut de Physique Nucléaire, IN2P3-CNRS, Université Paris Sud, F-91406 Orsay, France. gibelin@lpccaen.in2p3.fr
Beaumel
D
D
Motobayashi
T
T
Blumenfeld
Y
Y
Aoi
N
N
Baba
H
H
Elekes
Z
Z
Fortier
S
S
Frascaria
N
N
Fukuda
N
N
Gomi
T
T
Ishikawa
K
K
Kondo
Y
Y
Kubo
T
T
Lima
V
V
Nakamura
T
T
Saito
A
A
Satou
Y
Y
Scarpaci
J-A
JA
Takeshita
E
E
Takeuchi
S
S
Teranishi
T
T
Togano
Y
Y
Vinodkumar
A M
AM
Yanagisawa
Y
Y
Yoshida
K
K