EURICA is a project at RIKEN Nishina Center aimed at studying a wide range of exotic nuclei through β-decay measurements and high-resolution γ-ray spectroscopy. The setup is located behind the ...BigRIPS fragment separator and the ZeroDegree spectrometer at the RIBF. EURICA consists of the HPGe cluster detectors from the previous Euroball and RISING projects, together with double-sided silicon-strip detectors for β-decay counting and lifetime measurements. In total, this setup provides us with the possibility to study several aspects of the exotic nuclei produced at the RIBF.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The dipole polarizability of stable even-mass tin isotopes 112,114,116,118,120,124Sn was extracted from inelastic proton scattering experiments at 295MeV under very forward angles performed at RCNP. ...Predictions from energy density functionals cannot account for the present data and the polarizability of 208Pb simultaneously. The evolution of the polarizabilities in neighboring isotopes indicates a kink at 120Sn while all model results show a nearly linear increase with mass number after inclusion of pairing corrections.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The isospin character of p-n pairs at large relative momentum has been observed for the first time in the ^{16}O ground state. A strong population of the J,T=1,0 state and a very weak population of ...the J,T=0,1 state were observed in the neutron pickup domain of ^{16}O(p,pd) at 392 MeV. This strong isospin dependence at large momentum transfer is not reproduced by the distorted-wave impulse approximation calculations with known spectroscopic amplitudes. The results indicate the presence of high-momentum protons and neutrons induced by the tensor interactions in the ground state of ^{16}O.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Neutron-rich Pm (Z=61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, RIKEN Nishina Center using the in-flight fission of a 345 MeV/nucleon 238U beam. A cluster-type Ge detector array, ...EURICA, was used to measure the delayed γ rays from stopped ions. Isomeric γ decays were observed in 159Pm and 161Pm with half-lives of 4.97(12) μs and 0.79(4) μs, respectively. Level schemes for 159Pm and 161Pm were constructed in this study. The isomeric states of 159Pm and 161Pm could be interpreted as two quasiparticle excitations of neutrons with the configurations of ν(7/2633⊗5/2523) and ν(7/2633⊗1/2521), respectively. They are analogous to the isomers that have been observed systematically in other even-mass N=98 and N=100 isotones in this region. A projected shell model calculation was performed and it reproduced the order of three-quasiparticle states only if new Nilsson parameters with an N-dependent spin-orbit interaction were used. This work demonstrates that the strength of spin-orbit interactions in standard Nilsson parameters needs to be modified to study the properties of neutron-rich rare-earth nuclei around A=165, and provides new evidence supporting the existence of the deformed N=98 subshell gap in odd-mass nuclei for the first time.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Isomeric states were observed in nuclei produced in an experiment at the RIKEN Nishina Center Radioactive Isotope Beam Factory following the in-flight fission of a 345 MeV/nucleon
238
U beam. Isomers ...reported in nuclei spanning a predicted prolate-oblate shape change boundary,
111
Zr (
E
=
283.1
keV;
τ
=
0.326
(
63
)
μ
s),
112
Nb (
E
=
44.2
keV;
τ
=
0.094
(
26
)
μ
s),
113
Nb (
E
=
135.4
keV;
τ
=
0.846
(
80
)
μ
s), and
115
Mo (
E
=
198.6
keV;
τ
=
63
(
4
)
μ
s), are compared to potential-energy surface calculations which gave a selection of low-lying configurations for each nucleus. Tentative assignments of ground and excited states were made based on energy similarities to the calculations, reduced transition probabilities of the decays, and constraints of transition multipolarities from
γ
-ray coincidence measurements. These assignments are suggestive of significant deformation being persistent for
N
>
70
in this region. In addition, isomers in
108
Nb,
109
Nb,
113
Tc,
117
Ru,
119
Ru,
120
Rh, and
122
Rh, not spanning the prolate-oblate transition discussed, are presented.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Nuclear matrix elements (NMEs) for double beta decays (DBDs) are crucial for studying the neutrino mass and other neutrino properties beyond the standard electro-weak model by measuring neutrino-less ...DBDs. The spin-dipole (SD) Jπ = 2− NME is one of the major components associated with the DBD NME. The SD NME for 76Ge was derived for the first time by using the 74,76 Ge (3He, t) at RCNP Osaka. The obtained SD NME for the 76Ge → 76As ground-state transition is M EXP − ( SD ) = 1.5 × 10 − 3 in natural units. This is smaller by a coefficient around k 0.2 with respect to the quasi-particle model NME M QP − ( SD ) . The impact of the reduced (quenched) SD NME on DBD neutrino studies is discussed.
The Gamow–Teller strength distributions of
116
Sb
and
122
Sb
were measured with the
116
,
122
Sn
(
3
He
,
t
)
116
,
122
Sb
charge-exchange reactions at
140
MeV/u
. The measurements were carried out ...at the Research Center for Nuclear Physics (RCNP) at Osaka University in Osaka, Japan using the Grand Raiden spectrometer. The data were analysed by Multipole-Decomposition Analysis (MDA). The Gamow–Teller strengths summed up to
28
MeV
are
(
38
±
7
)
%
and
(
48
±
6
)
%
of the Ikeda sum rule for
116
Sb
and
122
Sb
, respectively, if the quasi-free scattering (QFS) contribution is not subtracted. These percentages are
(
29
±
7
)
%
and
(
35
±
5
)
%
, respectively, if the QFS contribution is maximally subtracted. These results were compared to those from previous measurements of the same isotopes, to recent measurements of
150
Pm
, and to a Quasi-particle Random-Phase Approximation (QRPA) calculation with Quasi-Particle Vibration Coupling (QPVC). The data suggest that the true QFS contribution is small for
116
Sb
, but are inconclusive about whether the QFS contribution is small or significant for
122
Sb
. Therefore, these data may provide an interesting test for the general quenching phenomenon of the Gamow–Teller Resonance (GTR). However, more research to reveal the nature of the QFS contribution is still needed on both the experimental and the theoretical side.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The decay of a new four-quasiparticle isomeric state in 160Sm has been observed using γ-ray spectroscopy at the RIBF, RIKEN. The four-quasiparticle state is assigned a 2π⊗2νπ52−532, π52+413, ν52−523, ...ν72+633 configuration. The half-life of this (11+) state is measured to be 1.8(4) μs. The (11+) isomer decays into a rotational band structure, based on a (6−) ν52−523⊗ν72+633 bandhead, consistent with the gK−gR values. This decays to a (5−) two-proton quasiparticle state, which in turn decays to the ground state band. Potential energy surface and blocked-BCS calculations were performed in the deformed midshell region around 160Sm. They reveal a significant influence from β6 deformation and that 160Sm is the best candidate for the lightest four-quasiparticle K isomer to exist in this region. The relationship between reduced hindrance and isomer excitation energy for E1 transitions from multiquasiparticle states is considered with the new data from 160Sm. The E1 data are found to agree with the existing relationship for E2 transitions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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