1. Collective nature of low-lying excitations in Zn-70,Zn-72,Zn-74 from lifetime measurements using the AGATA spectrometer demonstrator
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Louchart, C., Obertelli, A., Goergen, A., Wolfram KORTEN, Bazzacco, D., Birkenbach, B., Bruyneel, B., Clement, E., Coleman-Smith, P. J., Corradi, L., Curien, D., Angelis, G., France, G., Delaroche, J. P., Dewald, A., Didierjean, F., Doncel, M., Duchene, G., Eberth, J., Erduran, M. N., Farnea, E., Finck, C., Fioretto, E., Fransen, C., Gadea, A., Girod, M., Gottardo, A., Grebosz, J., Habermann, T., Hackstein, M., Huyuk, T., Jolie, J., Judson, D., Jungclaus, A., Karkour, N., Klupp, S., Kruecken, R., Kusoglu, A., Lenzi, S. M., Libert, J., Ljungvall, J., Lunardi, S., Maron, G., Menegazzo, R., Mengoni, D., Michelagnoli, C., Million, B., Molini, P., Moeller, O., Montagnoli, G., Montanari, D., Napoli, D. R., Orlandi, R., Pollarolo, G., Prieto, A., Pullia, A., Quintana, B., Recchia, F., Reiter, P., Rosso, D., Rother, W., Sahin, E., Salsac, M. D., Scarlassara, F., Schlarb, M., Siem, S., Singh, P. P., Soderstrom, P. A., Stefanini, A. M., Stezowski, O., Sulignano, B., Szilner, S., Theisen, Ch, Ur, C. A., Valiente-Dobon, J. J., and Zielinska, M.
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Subatomär fysik ,Subatomic Physics - Abstract
WOS: 000318527400007 Background: Neutron-rich nuclei with protons in the fp shell show an onset of collectivity around N=40. Spectroscopic information is required to understand the underlying mechanism and to determine the relevant terms of the nucleon-nucleon interaction that are responsible for the evolution of the shell structure in this mass region. Methods: We report on the lifetime measurement of the first 2(+) and 4(+) states in Zn-70,Zn-72 ,Zn-74 and the first 6(+) state in Zn-72 using the recoil distance Doppler shift method. The experiment was carried out at the INFN Laboratory of Legnaro with the AGATA demonstrator, first phase of the Advanced Gamma Tracking Array of highly segmented, high-purity germanium detectors coupled to the PRISMA magnetic spectrometer. The excited states of the nuclei of interest were populated in the deep inelastic scattering of a Ge-76 beam impinging on a U-238 target. Results: The maximum of collectivity along the chain of Zn isotopes is observed for Zn-72 at N=42. An unexpectedly long lifetime of 20(-5.2)(+1.8) ps was measured for the 4(+) state in Zn-74. Conclusions: Our results lead to small values of the B(E2;4(1)(+) -> 21(+))/B(E2;2(1)(+->)0(1)(+)) ratio for Zn-72,Zn-74, suggesting a significant noncollective contribution to these excitations. These experimental results are not reproduced by state-of-the-art microscopic models and call for lifetime measurements beyond the first 2(+) state in heavy zinc and nickel isotopes. European Union Seventh Framework Program FP7/2007-2013 [DPN/N190/AGATA/2009]; Polish MNiSW [DPN/N190/AGATA/2009]; Spanish Ministerio de Ciencia e Innovacion [FPA2011-29854-C04]; BMBF [05P12RDFN8, 06DA9040I]; [262010 ENSAR]; Science and Technology Facilities Council [ST/F004052/1, ST/J000108/1] The authors are grateful to the ALPI accelerator team for quality of the beam delivered during the experiment. B. Lommel and J. Steiner from the GSI are acknowledged for their help in preparing the Uranium target and the opportunity to use the GSI target laboratory. The authors would like to thank F. Nowacki and K. Sieja for enlightening discussions and their suggestions to improve the manuscript. This work has been partly financed by the European Union Seventh Framework Program FP7/2007-2013 under Grant Agreement No. 262010 ENSAR, the Polish MNiSW under Grant No. DPN/N190/AGATA/2009, the Spanish Ministerio de Cienciae Innovacion under Contract No. FPA2011-29854-C04, and the BMBF under Grant Nos. 05P12RDFN8 and 06DA9040I.
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- 2013