
Z Elekes,
Zs Dombrádi,
N Aoi,
H Baba,
S Bishop,
K Demichi,
Zs Fülöp,
J Gibelin,
T Gomi,
H Hasegawa,
[......],
D Suzuki,
M Suzuki,
H Takeda,
E Takeshita,
S Takeuchi,
M Tamaki,
Y Togano,
K Yamada,
Y Yanagisawa,
K Yoneda
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ABSTRACT:
The behavior of the nuclear shell structure far away from the valley of stability is discussed in this paper with an emphasis on the N = 20 magic number. Two experimental examples, namely γspectroscopy of 27Ne by 1H(28Ne, 27Ne) reaction and singleparticle spectroscopy of 23O by 22O(d, p)23O* → 22O+n process in inverse kinematics, are shown providing indirect indication and a direct evidence for the extreme decrease of the N = 20 shell gap and, consequently, the vanishing N = 20 magicity.
Journal of Physics G Nuclear and Particle Physics 12/2007; 35(1):014038. DOI:10.1088/09543899/35/1/014038 · 2.84 Impact Factor

Z. Elekes,
Zs. Dombrádi,
A. Saito,
N. Aoi,
H. Baba,
K. Demichi,
Zs. Fülöp,
J. Gibelin,
T. Gomi,
H. Hasegawa,
[......],
H. K. Sakai,
H. Sakurai,
S. Shimoura,
E. Takeshita,
S. Takeuchi,
M. Tamaki,
Y. Togano,
K. Yamada,
Y. Yanagisawa,
K. Yoneda
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ABSTRACT:
This paper reports on the 1H(28Ne,28Ne) and 1H(28Ne,27Ne)
reactions studied at intermediate energy using a liquid hydrogen target. From
the cross section populating the first 2+ excited state of 28Ne, and using the previously
determined B(E2) value, the neutron quadrupole transition matrix element has been
calculated to be Mn=13.8 ±3.7 fm2.
In the neutron knockout reaction, two lowlying excited states were populated in 27Ne.
Only one of them can be interpreted by the sd shell model while the additional state
may intrude from the fp shell. These experimental observations
are consistent with the presence of fp shell configurations at low excitation energy
in 27,28Ne nuclei caused by a vanishing N=20 shell gap at Z=10.
The European Physical Journal Special Topics 10/2007; 150(1):99102. DOI:10.1140/epjst/e2007002775 · 1.76 Impact Factor

Zs Dombrádi,
Z Elekes,
A Saito,
N Aoi,
H Baba,
K Demichi,
Zs Fülöp,
J Gibelin,
T Gomi,
H Hasegawa,
[......],
H K Sakai,
H Sakurai,
S Shimoura,
E Takeshita,
S Takeuchi,
M Tamaki,
Y Togano,
K Yamada,
Y Yanagisawa,
K Yoneda
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ABSTRACT:
Stucture of N = 17,18 nuclei has been investigated via proton inelastic scattering and neutron removal reactions up to the neutron dripline in inverse kinematics by use of radioctive ion beams provided by the RIKEN isotope separator, RIPS. Low energy excited states have been found in all the 26,27F and 27Ne nuclei, which are out of the neutron sd shell configuration space and are considered as intruder states arisng from cross shell excitations. MonteCarlo shell model calculations with the sdpfm interaction predict low energy negative parity excited states from neutron cross shell excitation at N = 17,18, which is in agreement with our experimental results. Observation of intruder states even at N = 17, especially the p3/2 state in 27Ne at 765 keV is a clear indication of a vanishing N = 20 shell gap at Z = 8 as predicted by the sdpfm shell model calculations.
Journal of Physics Conference Series 11/2006; 49(1):140. DOI:10.1088/17426596/49/1/031

Zs Dombrádi,
Z Elekes,
A Saito,
N Aoi,
H Baba,
K Demichi,
Zs Fülöp,
J Gibelin,
T Gomi,
H Hasegawa,
[......],
H K Sakai,
H Sakurai,
S Shimoura,
E Takeshita,
S Takeuchi,
M Tamaki,
Y Togano,
K Yamada,
Y Yanagisawa,
K Yoneda
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ABSTRACT:
This Letter reports on the (1)H((28)Ne, (28)Ne) and (1)H((28)Ne, (27)Ne) reactions studied at intermediate energy using a liquid hydrogen target. From the cross section populating the first 2(+) excited state of (28)Ne, and using the previously determined BE(2) value, the neutron quadrupole transition matrix element has been calculated to be M(n)=13.8 +/ 3.7 fm(2). In the neutron knockout reaction, two lowlying excited states were populated in (27)Ne. Only one of them can be interpreted by the sd shell model while the additional state may intrude from the fp shell. These experimental observations are consistent with the presence of fp shell configurations at low excitation energy in (27,28)Ne nuclei caused by a vanishing N=20 shell gap at Z=10.
Physical Review Letters 06/2006; 96(18):182501. DOI:10.1103/PhysRevLett.96.182501 · 7.73 Impact Factor

Z. Elekes,
Zs. Dombrádi,
A. Saito,
N. Aoi,
H. Baba,
K. Demichi,
Zs. Fülöp,
J. Gibelin,
T. Gomi,
H. Hasegawa,
[......],
H. K. Sakai,
H. Sakurai,
S. Shimoura,
E. Takeshita,
S. Takeuchi,
M. Tamaki,
Y. Togano,
K. Yamada,
Y. Yanagisawa,
K. Yoneda
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ABSTRACT:
The paper reports on the 30,31Na and 33,34Mg proton inelastic scattering reactions studied at intermediate energy. The neutron and proton deformation of the four nuclei have been deduced and found to be strongly correlated by comparing the present (p,p') data with that of previous Coulomb excitation experiments. In the neutronknockout channel a new state was found in 30Na at 360 keV and the energies of the known γray transitions have been confirmed in all the four nuclei.
Physical Review C 04/2006; 73(4). DOI:10.1103/PhysRevC.73.044314 · 3.88 Impact Factor

H. J. Ong,
N. Imai,
N. Aoi,
H. Sakurai,
Zs. Dombrádi,
A. Saito,
Z. Elekes,
H. Baba,
K. Demichi,
Z. S. Fülöp,
[......],
S. Ota,
H. K. Sakai,
S. Shimoura,
E. Takeshita,
S. Takeuchi,
M. Tamaki,
Y. Togano,
K. Yamada,
Y. Yanagisawa,
K. Yoneda
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ABSTRACT:
Inelastic proton scattering to the 21+ state of neutronrich 16C is studied in inverse kinematics using a 33MeV/nucleon beam. The deformation parameter βpp'=0.47(5) obtained is consistent with the global systematics of eveneven nuclei, based on the homogeneous quantum liquiddrop model. This result contrasts that of a recent lifetime measurement for the 21+ state in 16C, where an anomalously reduced E2 transition strength is observed. A combination of these two results yields a large Mn/Mp ratio of about 7, indicating a dominant neutron contribution to the quadrupole collectivity.

HJ Ong,
N Imai,
N Aoi,
H Sakurai,
Zs. Dombradi,
A Saito,
Z Elekes,
H Baba,
K Demichi,
Zs. Fulop,
[......],
S Ota,
HK Sakai,
S Shimoura,
E Takeshita,
S Takeuchi,
M Tamaki,
Y Togano,
K Yamada,
Y Yanagisawa,
K Yoneda
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ABSTRACT:
We have studied the 2+1 state in neutronrich 16Cvia inelastic proton scattering in inverse kinematics, using a 33 MeV/nucleon beam. From the angleintegrated crosssection, the deformation parameter βpp’ = 0.50(8) is obtained. This value is greater than the deformation parameter deduced from the lifetime measurement. With these two result combined, the ratio of the neutron and proton quadrupole matrix elements is deduced to be approximately 7, indicating a neutrondominant quadrupole collectivity in 16C.
European Physical Journal A 01/2005; 25:Supplement 1, 347. DOI:10.1140/epjad/i2005060566 · 2.42 Impact Factor

Z. Elekes,
Zs. Dombrádi,
A. Saito,
N. Aoi,
H. Baba,
K. Demichi,
Zs. Fülöp,
J. Gibelin,
T. Gomi,
H. Hasegawa,
[......],
H.K. Sakai,
H. Sakurai,
S. Shimoura,
E. Takeshita,
S. Takeuchi,
M. Tamaki,
Y. Togano,
K. Yamada,
Y. Yanagisawa,
K. Yoneda
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ABSTRACT:
The 1H(27F, 25,26,27F) reactions have been studied at 40 MeV/nucleon average energy using a liquid hydrogen target. For 25F, 26F and 27F nuclei, we have observed two γray peaks each originating from the decay of two bound excited states. This is the first sign of the existence of bound excited states in 26,27F. The presence of a single bound excited state in 27F is a clear indication of a substantial change in the structure of the fluorine isotopes approaching the neutron dripline. The proposed second excited states in 25,26,27F nuclei have no counterparts in either the psd or the sdpf shell model calculations suggesting the appearance of nuclear structure effects lying out of these model spaces.

Z Elekes,
Zs. Dombradi,
A Saito,
N Aoi,
H Baba,
K Demichi,
Zs. Fulop,
J Gibelin,
T Gomi,
H Hasegawa,
[......],
H K Sakai,
H Sakurai,
S Shimoura,
E Takeshita,
S Takeuchi,
M Tamaki,
Y Togano,
K Yamada,
Y Yanagisawa,
K Yoneda