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J. Robin,
Th. Byrski,
G. Duchêne,
F.A. Beck,
D. Curien,
N. Dubray,
J. Dudek,
A. Góźdź,
A. Odahara,
N. Schunck, [......],
E. S. Paul,
C. Petrache,
I. Piqueras,
N Redon,
A. Saltarelli,
J Simpson,
O. Stezowski,
R. Venturelli,
J.P. Vivien,
K Zuber
[show abstract]
[hide abstract]
ABSTRACT: A detailed study of known and new SD bands in Tb isotopes has been performed with the use of the EUROBALL IV gamma-ray array. The high-statistics data set has allowed for the extension of known SD bands at low and high spins by new gamma-ray transitions. These transitions, as it turns out, correspond to the rotational frequencies where the principal superdeformed gaps (Z=66,N=86) close giving rise to up- or down-bending mechanisms. This enables to attribute the underlying theoretical configurations with much higher confidence as compared to the previous identifications. Five new SD bands have been discovered, three of them assigned to the 152Tb and the two others to the 151Tb nuclei. Nuclear mean-field calculations have been used to interpret the structure of known SD bands as well as of the new ones in terms of nucleonic configurations.
Papers from the Department of Physics. 05/2013;
-
M. Kmiecik,
A. Maj,
M. Brekiesz,
K. Mazurek,
P. Bednarczyk,
J. Grebosz,
W. Meczynski,
J. Styczen,
M. Zieblinski,
K Zuber, [......],
M. Rousseau,
J. Dudek,
N. Schunck, A. Bracco,
F. Camera,
G. Benzoni,
O. Wieland,
B Herskind,
E. Farnea,
G De Angelis
-
A Gottardo,
J J Valiente-Dobón,
G Benzoni,
R Nicolini,
A Gadea,
S Lunardi,
P Boutachkov,
A M Bruce,
M Górska,
J Grebosz, [......],
P Strmen,
T P D Swan,
I Szarka,
C A Ur,
P M Walker,
O Wieland,
H-J Wollersheim,
F Nowacki,
E Maglione,
A P Zuker
[show abstract]
[hide abstract]
ABSTRACT: The neutron-rich lead isotopes, up to ^{216}Pb, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond ^{208}Pb.
Physical Review Letters 10/2012; 109(16):162502. · 7.37 Impact Factor
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G. Benzoni,
A.I. Morales,
J.J. Valiente-Dobón,
A. Gottardo, A. Bracco,
F. Camera,
F.C.L. Crespi,
A.M. Corsi,
S. Leoni,
B. Million, [......],
A. Sharma,
B. Sitar,
D. Siwal,
K. Steiger,
P. Strmen,
T.P.D. Swan,
I. Szarka,
C.A. Ur,
P.M. Walker,
H.-J. Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: Neutron-rich isotopes around lead, beyond N = 126 , have been studied exploiting the fragmentation of an uranium primary beam at the FRS-RISING setup at GSI. For the first time β-decay half-lives of Bi 219 and Tl 211 , 212 , 213 isotopes have been derived. The half-lives have been extracted using a numerical simulation developed for experiments in high-background conditions. Comparison with state of the art models used in r-process calculations is given, showing a systematic underestimation of the experimental values, at variance from close-lying nuclei.
Physics Letters B 09/2012; 715(4–5):293-297. · 3.95 Impact Factor
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F. C. L. Crespi,
R. Avigo,
F. Camera,
S. Akkoyun,
A. Atac,
D. Bazzacco,
M. Bellato,
G. Benzoni,
N. Blasi,
D. Bortolato, [......],
L. Pellegri,
F. Recchia,
P. Reiter,
S. Riboldi,
C. A. Ur,
V. Vandone,
J. J. Valiente-Dobon,
O. Wieland,
A. Wiens,
The AGATA Collaboration
[show abstract]
[hide abstract]
ABSTRACT: The response of AGATA segmented HPGe detectors to gamma rays in the energy
range 2-15 MeV was measured. The 15.1 MeV gamma rays were produced using the
reaction d(11B,ng)12C at Ebeam = 19.1 MeV, while gamma-rays between 2 to 9 MeV
were produced using an Am-Be-Fe radioactive source. The energy resolution and
linearity were studied and the energy-to-pulse-height conversion resulted to be
linear within 0.05%. Experimental interaction multiplicity distributions are
discussed and compared with the results of Geant4 simulations. It is shown that
the application of gamma-ray tracking allows a suppression of background
radiation following neutron capture by Ge nuclei. Finally the Doppler
correction for the 15.1 MeV gamma line, performed using the position
information extracted with Pulse-shape Analysis, is discussed.
09/2012;
-
S. Bottoni,
G. Benzoni,
S. Leoni,
D. Montanari, A. Bracco,
F. Azaiez,
S. Franchoo,
I. Stefan,
N. Blasi,
F. Camera, [......],
C. Ur,
F. Scarlassara,
A. Gadea,
A. Maj,
J. Wrzesinski,
K. Zuber,
Zs. Dombradi,
S. Szilner,
A. Saltarelli,
G. Pollarolo
[show abstract]
[hide abstract]
ABSTRACT: The heavy-ion reaction 22Ne+208Pb at 128 MeV beam energy has been studied using the PRISMA-CLARA experimental setup at Legnaro National Laboratories. Elastic, inelastic, and one-nucleon transfer differential cross sections are measured and global agreement is obtained with semiclassical and distorted-wave Born approximation (DWBA) calculations. In particular, the angular distribution of the 2+ state of 22Ne is analyzed by DWBA and a similar calculation is performed for the unstable 24Ne nucleus, using existing data from the reaction 24Ne+208Pb at 182 MeV (measured at SPIRAL with the VAMOS-EXOGAM setup). In both cases the DWBA model gives a good reproduction of the experiment, pointing to a strong reduction of the β2C charge deformation parameter in 24Ne. This follows the trend predicted for the evolution of the quadrupole deformation along the Ne isotopic chain.
Phys. Rev. C. 06/2012; 85(6).
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F. Recchia,
S. M. Lenzi,
S. Lunardi,
E. Farnea,
A. Gadea,
N. Mărginean,
D. R. Napoli,
F. Nowacki,
A. Poves,
J. J. Valiente-Dobón, [......],
G. Montagnoli,
R. Orlandi,
G. Pollarolo,
E. Sahin,
F. Scarlassara,
R. P. Singh,
A. M. Stefanini,
S. Szilner,
C. A. Ur,
O. Wieland
[show abstract]
[hide abstract]
ABSTRACT: The neutron-rich cobalt isotopes up to A=67 have been studied through multinucleon transfer reactions by bombarding a 238U target with a 460-MeV 70Zn beam. Unambiguous identification of prompt γ rays belonging to each nucleus has been achieved using coincidence relationships with the ions detected in a high-acceptance magnetic spectrometer. The new data are discussed in terms of the systematics of the cobalt isotopes and interpreted with large-scale shell-model calculations in the fpgd model space. In particular, very different shapes can be described in 67Co, at the edge of the island of inversion at N=40, where a low-lying highly deformed band coexists with a spherical structure.
Phys. Rev. C. 06/2012; 85(6).
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A. Krasznahorkay,
L. Stuhl,
M. Csatlós,
A. Algora,
J. Gulyás,
J. Timár,
N. Paar,
D. Vretenar,
K. Boretzky,
M. Heil, [......],
V. Volkov,
F. Wamers,
E. Fiori,
B. Löher,
J. Marganiec,
D. Savran,
H. T. Johansson,
P. Diaz Fernández,
U. Garg,
D. L. Balabanski
[show abstract]
[hide abstract]
ABSTRACT: The gamma-decay of the anti-analog of the giant dipole resonance (AGDR) has
been measured to the isobaric analog state excited in the p(124Sn,n) reaction
at a beam energy of 600 MeV/nucleon. The energy of the transition was also
calculated with state-of-the-art self-consistent random-phase approximation
(RPA) and turned out to be very sensitive to the neutron-skin thickness
(\DeltaR_(pn)). By comparing the theoretical results with the measured one, the
\DeltaR_(pn) value for 124Sn was deduced to be 0.175 \pm 0.048 fm, which agrees
well with the previous results. The energy of the AGDR measured previously for
^(208)Pb was also used to determine the \DeltaR_(pn) for ^(208)Pb. In this way
a very precise \DeltaR_(pn) = 0.181 \pm 0.031 neutron-skin thickness has been
obtained for 208Pb. The present method offers new possibilities for measuring
the neutron-skin thicknesses of very exotic isotopes.
05/2012;
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M. Fantuzi,
C. M. Petrache,
D. Mengoni,
M. Axiotis,
D. Bazzacco,
G. Benzoni,
P. G. Bizzeti,
A. M. Bizzeti-Sona,
N. Blasi, A. Bracco, [......],
N. Marginean,
R. Menegazzo,
D. R. Napoli,
M. Nespolo,
P. Pavan,
C. Rossi Alvarez,
P. Spolaore,
C. A. Ur,
R. Venturelli,
F. R. Xu
[show abstract]
[hide abstract]
ABSTRACT: Excited states in the very neutron-deficient122La nucleus have been established for the first time using the92Mo(40Ca, 2α1p1n) reaction at beam energies of 190 and 200MeV. The observed transitions were grouped in three bands. Configurations have been
assigned to the observed bands based on the properties extracted from the experimental data and on cranked shell model calculations.
European Physical Journal A 04/2012; 38(1):43-51. · 2.19 Impact Factor
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M. Kmiecik,
A. Maj,
J. Gerl,
G. Neyens,
L. Atanasova,
D. L. Balabanski,
F. Becker,
P. Bednarczyk,
G. Benzoni,
N. Blasi, [......],
N. Saito,
T. R. Saito,
A. Saltarelli,
G. S. Simpson,
J. Styczeń,
N. Vermeulen,
E. Werner-Malento,
O. Wieland,
H. J. Wollersheim,
M. Ziȩbliński
[show abstract]
[hide abstract]
ABSTRACT: The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV Ip=12+\ensuremath I^{\pi}=12^+ isomer in 192Pb with t \tau = 1.57 μs has been produced using the fragmentation of a 1A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with
a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the
maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured
values of the lifetime, t \tau = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.
European Physical Journal A 04/2012; 45(2):153-158. · 2.19 Impact Factor
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S. Akkoyun,
A. Algora,
B. Alikhani,
F. Ameil,
G. de Angelis,
L. Arnold,
A. Astier,
A. Ataç,
Y. Aubert,
C. Aufranc, [......],
D. Weisshaar,
D. Wells,
O. Wieland,
A. Wiens,
G. Wittwer,
H. J. Wollersheim,
F. Zocca,
N. V. Zamfir,
M. Ziȩbliński,
A. Zucchiatti
[show abstract]
[hide abstract]
ABSTRACT: The Advanced GAmma Tracking Array (AGATA) is a European project to develop
and operate the next generation gamma-ray spectrometer. AGATA is based on the
technique of gamma-ray energy tracking in electrically segmented high-purity
germanium crystals. This technique requires the accurate determination of the
energy, time and position of every interaction as a gamma ray deposits its
energy within the detector volume. Reconstruction of the full interaction path
results in a detector with very high efficiency and excellent spectral
response. The realization of gamma-ray tracking and AGATA is a result of many
technical advances. These include the development of encapsulated
highly-segmented germanium detectors assembled in a triple cluster detector
cryostat, an electronics system with fast digital sampling and a data
acquisition system to process the data at a high rate. The full
characterization of the crystals was measured and compared with
detector-response simulations. This enabled pulse-shape analysis algorithms, to
extract energy, time and position, to be employed. In addition, tracking
algorithms for event reconstruction were developed. The first phase of AGATA is
now complete and operational in its first physics campaign. In the future AGATA
will be moved between laboratories in Europe and operated in a series of
campaigns to take advantage of the different beams and facilities available to
maximize its science output. The paper reviews all the achievements made in the
AGATA project including all the necessary infrastructure to operate and support
the spectrometer.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 11/2011; 668:26. · 1.21 Impact Factor
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D. Montanari,
S. Leoni,
L. Corradi,
G. Pollarolo,
G. Benzoni,
N. Blasi,
S. Bottoni, A. Bracco,
F. Camera,
A. Corsi, [......],
S. Lunardi,
G. Montagnoli,
F. Scarlassara,
C. Ur,
G. Lo Bianco,
A. Zucchiatti,
S. Szilner,
M. Kmiecik,
A. Maj,
W. Meczynski
[show abstract]
[hide abstract]
ABSTRACT: Elastic, inelastic, and one-nucleon transfer channels in the 48Ca + 64Ni reaction have been measured at ≈6 MeV/nucleon with the PRISMA-CLARA setup, at Legnaro National Laboratory, consisting of the coupling of a large solid angle magnetic spectrometer with a germanium array. By trajectory reconstruction the reaction products have been fully identified in mass, nuclear charge, and kinetic energy, while coincident γ spectra of binary partners have been constructed after Doppler correction. Absolute differential cross sections have been extracted for the inelastic excitation and one-nucleon transfer, also for specific excited states. The data are in good agreement with semiclassical calculations and distorted wave Born approximation predictions. The work outlines an experimental method which can become valuable to extract structural information from heavy-ion reaction studies.
Phys. Rev. C. 11/2011; 84(5).
-
H. Watanabe,
K. Yamaguchi,
A. Odahara,
T. Sumikama,
S. Nishimura,
K. Yoshinaga,
Z. Li,
Y. Miyashita,
K. Sato,
L. Próchniak, [......],
D. Steppenbeck,
K. Sugimoto,
K. Tajiri,
S. Takano,
A. Takashima,
T. Teranishi,
Y. Wakabayashi,
P.M. Walker,
O. Wieland,
H. Yamaguchi
[show abstract]
[hide abstract]
ABSTRACT: The neutron-rich nucleus 110Mo has been investigated by means of γ-ray spectroscopy following the β-decay of 110Nb, produced using in-flight fission of a 238U beam at 345 MeV/nucleon at the RIBF facility. In addition to the ground-band members reported previously, spectroscopic information on the low-lying levels of the quasi-γ band built on the second 2+ state at 494 keV has been obtained for the first time. The experimental finding of the second 2+ state being lower than the yrast 4+ level suggests that axially-asymmetric γ softness is substantially enhanced in this nucleus. The experimental results are compared with model calculations based on the general Bohr Hamiltonian method. The systematics of the low-lying levels in even–even A≈110 nuclei is discussed in comparison with that in the neutron-rich A≈190 region, by introducing the quantity , , as a global signature of the structural evolution involving axial asymmetry.
Physics Letters B 10/2011; 704(4):270-275. · 3.95 Impact Factor
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A Bracco
[show abstract]
[hide abstract]
ABSTRACT: The Coulomb excitation of the neutron rich 68Ni was measured using it as as secondary radioactive beam at 600 MeV/nucleon impinging on a 197Au target. The dipole strength in the region at around the nucleon binding energy was extracted from the gamma decay measurement. A sizable fraction of "pygmy" dipole strength, energetically located below the giant dipole resonance, is observed in this nucleus. The experimental data is discussed in connection with predictions obtained using different Random Phase Approximation (RPA) models for the dipole response, based on a representative set of Skyrme effective forces plus meson-exchange effective Lagrangians. A comparison with the experimental data for both 68Ni and 132Sn has allowed us to constrain the value of the derivative of the symmetry energy at saturation. The neutron skin radius is deduced under this constraint.
Journal of Physics Conference Series 09/2011; 312(9):092005.
-
S Leoni,
D Montanari,
G Benzoni,
N Blasi,
G Bocchi, A Bracco,
F Camera,
A Corsi,
F C L Crespi,
B Million, [......],
D Mengoni,
G Montagnoli,
F Scarlassara,
C Ur,
G Lo Bianco,
A Zucchiatti,
M Kmiecik,
A Maj,
W Meczynski,
G Pollarolo
[show abstract]
[hide abstract]
ABSTRACT: The population and gamma decay of neutron rich nuclei around 48Ca has been measured at Legnaro National Laboratory with the PRISMA-CLARA setup, using deep-inelastic collisions (DIC) on 64Ni, at an energy approximately twice the Coulomb barrier. The reaction properties of the main products are investigated, focusing on total cross sections and angular distributions both integrated in energy and associated to the population of specific excited states. Gamma spectroscopy studies are also performed, giving evidence, for the first time in transfer reactions with heavy ions, of a large spin alignment (~70%), perpendicular to the reaction plane. This makes possible the use of angular distributions and polarization measurements to firmly establish the spin and parity of excited states populated in nucleon transfer channels, as in the case of 49Ca, where candidates for particle-core coupling are investigated. Both reaction and gamma spectroscopy studies demonstrate the relevance of DIC with heavy ions for a detailed investigation of moderately neutron rich systems.
Journal of Physics Conference Series 09/2011; 312(9):092037.
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A Gottardo,
J J Valiente-Dobón,
G Benzoni,
R Nicolini,
J Alcántara Núñez,
A Algora,
N Al-Dahan,
G de Angelis,
Y Ayyad,
N Alkhomashi, [......],
B Sitar,
D Siwal,
K Steger,
P Strmen,
T P D Swan,
I Szarka,
P M Walker,
O Wieland,
H Weick,
H-J Wollersheim
[show abstract]
[hide abstract]
ABSTRACT: Neutron-rich nuclei beyond N = 126 in the lead region were populated by fragmenting a 238U beam at 1 GeV A on a Be target and then separated by the Fragment Separator (FRS) at GSI. Their isomeric decays were observed, enabling study of the shell structure of neutron-rich nuclei around the Z=82 shell closure. Some preliminary results are reported in this paper.
Journal of Physics Conference Series 09/2011; 312(9):092026.
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H Watanabe,
K Yamaguchi,
A Odahara,
T Sumikama,
S Nishimura,
K Yoshinaga,
Z Li,
Y Miyashita,
K Sato,
L Prochniak, [......],
D Steppenbeck,
K Sugimoto,
K Tajiri,
S Takano,
A Takashima,
T Teranishi,
Y Wakabayashi,
P M Walker,
O Wieland,
H Yamaguchi
[show abstract]
[hide abstract]
ABSTRACT: {{The neutron-rich nucleus Mo-110 has been investigated by means of gamma-ray spectroscopy following the beta-decay of Nb-110, produced using in-flight fission of a U-238 beam at 345 MeV/nucleon at the RIBF facility. In addition to the ground-band members reported previously, spectroscopic information on the low-lying levels of the quasi-gamma band built on the second 2(+) state at 494 key has been obtained for the first time. The experimental finding of the second 2(+) state being lower than the yrast 4(+) level suggests that axially-asymmetric gamma softness is substantially enhanced in this nucleus. The experimental results are compared with model calculations based on the general Bohr Hamiltonian method. The systematics of the low-lying levels in even-even A approximate to 110 nuclei is discussed in comparison with that in the neutron-rich A approximate to 190 region, by introducing the quantity E-S/E(2(1)(+))
Physics Letters B 09/2011; 704:270-275. · 3.95 Impact Factor
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Purnima Singh,
Somnath Nag,
A. K. Singh,
I. Ragnarsson,
H. Hübel,
A. Al-Khatib,
P. Bringel,
C. Engelhardt,
A. Neußer-Neffgen,
G. B. Hagemann, [......],
G. Benzoni,
F. Camera,
P. Fallon,
R. M. Clark,
M. P. Carpenter,
R. V. F. Janssens,
T. L. Khoo,
T. Lauritsen,
P. Chowdhury,
H. Amro
[show abstract]
[hide abstract]
ABSTRACT: High-spin states in 125I have been investigated using the reaction 82Se(48Ca, p4n) at a beam energy of 200 MeV and γ-ray coincidence events were detected using the Gammasphere spectrometer. A deformed rotational band, extending up to Iπ=95/2−, was observed for the first time in a heavier odd-A iodine nucleus. The characteristics of the band are very similar to those of the highly deformed bands observed recently in neighboring nuclei and it is essentially identical to one of the previously known bands in 126Xe. The experimental results are compared to cranked Nilsson-Strutinsky calculations and possible configurations for the band are discussed.
Phys. Rev. C. 08/2011; 84(2).
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T Sumikama,
K Yoshinaga,
H Watanabe,
S Nishimura,
Y Miyashita,
K Yamaguchi,
K Sugimoto,
J Chiba,
Z Li,
H Baba, [......],
K Steiger,
D Steppenbeck,
S Takano,
A Takashima,
K Tajiri,
T Teranishi,
Y Wakabayashi,
P M Walker,
O Wieland,
H Yamaguchi
[show abstract]
[hide abstract]
ABSTRACT: The low-lying states in ¹⁰⁶Zr and ¹⁰⁸Zr have been investigated by means of β-γ and isomer spectroscopy at the radioactive isotope beam factory (RIBF), respectively. A new isomer with a half-life of 620 ± 150 ns has been identified in ¹⁰⁸Zr. For the sequence of even-even Zr isotopes, the excitation energies of the first 2⁺ states reach a minimum at N = 64 and gradually increase as the neutron number increases up to N = 68, suggesting a deformed subshell closure at N = 64. The deformed ground state of ¹⁰⁸Zr indicates that a spherical subshell gap predicted at N = 70 is not large enough to change the ground state of ¹⁰⁸Zr to the spherical shape. The possibility of a tetrahedral shape isomer in ¹⁰⁸Zr is also discussed.
Physical Review Letters 05/2011; 106(20):202501. · 7.37 Impact Factor
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T Sumikama,
K Yoshinaga,
H Watanabe,
S Nishimura,
Y Miyashita,
K Yamaguchi,
K Sugimoto,
J Chiba,
Z Li,
H Baba, [......],
K Steiger,
D Steppenbeck,
S Takano,
A Takashima,
K Tajiri,
T Teranishi,
Y Wakabayashi,
P M Walker,
O Wieland,
H Yamaguchi
05/2011;
