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Author |
Delafosse, C. et al; Gadea, A.; Perez-Vidal, R.M.; Domingo-Pardo, C. |
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Title |
Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region: A Hint from Lifetime Measurements |
Type |
Journal Article |
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Year |
2018 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
121 |
Issue |
19 |
Pages |
192502 - 7pp |
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Abstract |
Lifetime measurements of excited states of the light N = 52 isotones Kr-88, Se-86, and Ge-84 have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B(E2; 2(+)-> 0(+)) and B(E2; 4(+)-> 2(+)) were obtained for the first time for the hard-to-reach 84Ge. While the B(E2; 2(+)-> 0(+) ) values of Kr-88, Se-86 saturate the maximum quadrupole collectivity offered by the natural valence (3s, 2d, 1g(7/2), 1h(11/2)) space of an inert Ni-78 core, the value obtained for Ge-84 largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N less than or similar to 49, extend beyond N = 50. The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector rho field in shell-structure evolution. |
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Address  |
[Delafosse, C.; Verney, D.; Marevic, P.; Gottardo, A.; Babo, M.; Franchoo, S.; Ibrahim, F.; Matea, I; Olivier, L.; Portail, C.; Stefan, I] Univ Paris Saclay, Univ Paris Sud, CNRS IN2P3, Inst Phys Nucl, F-91406 Orsay, France, Email: verney@ipno.in2p3.fr |
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Publisher |
Amer Physical Soc |
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English |
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Original Title |
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Abbreviated Series Title |
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Series Volume |
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Edition |
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ISSN |
0031-9007 |
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Conference |
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Notes |
WOS:000449791600008 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3800 |
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Author |
de Angelis, G. et al; Gadea, A. |
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Title |
Shape isomerism and shape coexistence effects on the Coulomb energy differences in the N = Z nucleus As-66 and neighboring T=1 multiplets |
Type |
Journal Article |
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Year |
2012 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
85 |
Issue |
3 |
Pages |
034320 - 7pp |
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Keywords |
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Abstract |
Excited states of the N = Z = 33 nucleus As-66 have been populated in a fusion-evaporation reaction and studied using gamma-ray spectroscopic techniques. Special emphasis was put into the search for candidates for the T = 1 states. A new 3(+) isomer has been observed with a lifetime of 1.1(3) ns. This is believed to be the predicted oblate shape isomer. The excited levels are discussed in terms of the shell model and of the complex excited Vampir approaches. Coulomb energy differences are determined from the comparison of the T = 1 states with their analog partners. The unusual behavior of the Coulomb energy differences in the A = 70 mass region is explained through different shape components (oblate and prolate) within the members of the same isospin multiplets. This breaking of the isospin symmetry is attributed to the correlations induced by the Coulomb interaction. |
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Address |
[de Angelis, G.; Martinez, T.; Orlandi, R.; Sahin, E.; Valiente-Dobon, J. J.; Gottardo, A.; Napoli, D. R.] Ist Nazl Fis Nucl, Lab Nazl Legnaro, I-35020 Padua, Italy |
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Publisher |
Amer Physical Soc |
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English |
Summary Language |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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ISSN |
0556-2813 |
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Conference |
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Notes |
WOS:000301706400003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
940 |
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Author |
AGATA Collaboration (Crespi, F.C.L. et al); Gadea, A. |
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Title |
Isospin Character of Low-Lying Pygmy Dipole States in Pb-208 via Inelastic Scattering of O-17 Ions |
Type |
Journal Article |
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Year |
2014 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
113 |
Issue |
1 |
Pages |
012501 - 5pp |
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Keywords |
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Abstract |
The properties of pygmy dipole states in Pb-208 were investigated using the Pb-208(O-17, O-17'gamma) reaction at 340 MeV and measuring the gamma decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted gamma rays and of the scattered particles were measured. The results are compared with (gamma, gamma') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2(+) and 3(-) states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1(-) excited states from 4 to 8 MeV. |
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Address |
[Crespi, F. C. L.; Bracco, A.; Nicolini, R.; Pellegri, L.; Leoni, S.; Avigo, R.; Bottoni, S.; Camera, F.; Ceruti, S.; Morales, A. I.; Vandone, V.; Pullia, A.] Univ Milan, Dipartimento Fis, I-20133 Milan, Italy, Email: angela.bracco@mi.infn.it |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0031-9007 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000338665200009 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1848 |
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Author |
AGATA Collaboration (Crespi, F.C.L. et al); Gadea, A. |
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Title |
1(-) and 2(+) discrete states in Zr-90 populated via the (O-17, O-17 'gamma) reaction |
Type |
Journal Article |
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Year |
2015 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
91 |
Issue |
2 |
Pages |
024323 - 9pp |
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Keywords |
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Abstract |
2(+) and 1(-) states in Zr-90 were populated via the (O-17, O-17 'gamma) reaction at 340 MeV. The gamma decay was measured with high resolution using the AGATA (advanced gamma tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2(+), 3(,)(-) and 1(-) states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1(-) state at 6.424 MeV. The comparison of the present (17O, 17O 'gamma) data with existing (gamma,gamma') and (p, p') data in the corresponding region of the gamma continuum (6-11 MeV), characterized by a large E1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy. |
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Address |
[Crespi, F. C. L.; Bracco, A.; Nicolini, R.; Leoni, S.; Bottoni, S.; Camera, F.; Corsi, A.; Pellegri, L.; Vandone, V.; Pullia, A.] Univ Milan, Dipartimento Fis, I-20133 Milan, Italy, Email: angela.bracco@mi.infn.it |
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Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0556-2813 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000350104800002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2147 |
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Author |
AGATA Collaboration (Crespi, F.C.L. et al); Gadea, A. |
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Title |
Response of AGATA segmented HPGe detectors to gamma rays up to 15.1 MeV |
Type |
Journal Article |
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Year |
2013 |
Publication |
Nuclear Instruments & Methods in Physics Research A |
Abbreviated Journal |
Nucl. Instrum. Methods Phys. Res. A |
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Volume |
705 |
Issue |
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Pages |
47-54 |
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Keywords |
AGATA; Gamma-ray spectroscopy; Gamma-ray tracking; HPGe detectors; Pulse-shape and gamma-ray tracking algorithms; Semiconductor detector performance and simulations |
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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(B-11,n gamma)C-12 at E-beam=19.1 MeV, while gamma rays between 2 and 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 caused by n-capture in 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. |
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Address |
[Crespi, F. C. L.; Avigo, R.; Camera, F.; Bottoni, S.; Bracco, A.; Ceruti, S.; Giaz, A.; Leoni, S.; Nicolini, R.; Pellegri, L.; Riboldi, S.; Vandone, V.] Univ Milan, Dipartimento Fis, I-20133 Milan, Italy, Email: fabio.crespi@mi.infn.it |
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Thesis |
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Publisher |
Elsevier Science Bv |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0168-9002 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000314826000009 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1329 |
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