The structure of low-lying 1− states in 90,94Zr from (α,α′γ) and (p,p′γ) reactions

Physics Letters B

N. Blasi¹  S. Zhu²  A. Tamii³  A. Bracco³  S. Bassauer³  M. Krzysiek⁴  T. Yamamoto⁵  A. Zilges⁶  J. Isaak⁷  P.J. Davies⁸  V. Derya⁹  M.K. Raju^1,10  Y. Yamamoto^1,11  E.G. Lanza^1,12  D.L. Balabanski^1,12  F.C.L. Crespi^1,12  J.J. Carroll^1,13  M. Weinert^1,14  N. Pietralla^1,15  L.M. Donaldson^1,15  S. Noji^1,15  F. Camera^1,16  N. Aoi^1,17  A.S. Brown^1,17  R.G.T. Zegers^1,18  M. Ciemała^1,18  B. Wasilewska^1,18  A. Maj^1,18  J.M. Schmitt^1,18  C. Sullivan^1,19  G. Gey^1,19  S.G. Pickstone^2,20  V. Werner^2,21  M. Spieker^2,21  X. Zhou^2,21  L. Morris^2,22  O. Wieland^2,22  Y.D. Fang^2,22  M.N. Harakeh^2,22  N. Ichige^2,22  G. Steinhilber^2,22  H.J. Ong^2,22  E. Ideguchi^2,22  M.P. Carpenter^2,22  T. Klaus^2,22  T. Koike^2,22  T. Hashimoto^2,22  A. Inoue^2,22  N. Kobayashi^2,22  C. Iwamoto^2,23  P. von Neumann Cosel^2,24  D.G. Jenkins^2,24  H.T. Ha^2,25  M. Liu^2,26  A. Czeszumska^2,26  H. Fujita^2,26  D. Savran^2,26 

[1] Corresponding author at: Dipartimento di Fisica dell'Università degli Studi di Milano, I-20133 Milano, Italy.;Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA;INFN, Sezione di Milano, I-20133 Milano, Italy;Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany;Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany;Joint Institute for Nuclear Astrophysics: Center for the Evolution of the Elements, Michigan State University, East Lansing, MI 48824, USA;University of Groningen, Zernikelaan 25, 9747 AA Groningen, the Netherlands;Argonne Natl. Lab., Div. Phys, Argonne, IL 60439 USA;CCDC/Army Research Laboratory, Adelphi, MD 20783, USA;Center for Nuclear Study, University of Tokyo, Tokyo 113-0033, Japan;Department of Physics, Florida State University, Tallahassee, FL 32306, USA;Dipartimento di Fisica dell'Università degli Studi di Milano, I-20133 Milano, Italy;ELI-NP, Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, 077125 Bucharest-Magurele, Romania;GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany;H. Niewodniczanski Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, PL-31342 Krakow, Poland;INFN, Sezione di Catania, I-95100 Catania, Italy;INFN, Sezione di Milano, I-20133 Milano, Italy;Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany;Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany;Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China;National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA;RCNP, Osaka Univ., Ibaraki, Osaka 5670047, Japan;Rare Isotope Science Project, Institute for Basic Science, Yuseong-gu, Daejeon 305-811, Republic of Korea;Tohoku Univ, Dept Phys, Sendai, Miyagi 9808578, Japan;Univ. Witwatersrand, Sch Phys, ZA-2050 Johannesburg, South Africa;Univ. of York, Dept. Phys., York YO10 5DD, N Yorkshire, England, United Kingdom;

关键词: Nuclear structure;    Dipole excitation around neutron threshold;    Inelastic scattering;   

DOI  :  

来源: DOAJ

【 摘 要 】

The low-lying dipole strength in the 90,94Zr nuclei was investigated via (p,p′γ) at 80 MeV and (α,α′γ) at 130 MeV. The experiments, made at RCNP, used the magnetic spectrometer Grand Raiden for the scattered particles and the array CAGRA with HPGe detectors for the γ-decay. For 94Zr these are the first data for both reactions and for 90Zr these are the first data with (p,p′γ) and the first ones at high resolution for (α,α′γ). The comparison of the present results for the two nuclei with existing (γ,γ′) data shows that both nuclear probes produce an excitation pattern different than that of the electromagnetic probes.DWBA calculations were made using form factors deduced from transition densities, based on RPA calculations, characterized by a strong neutron component at the nuclear surface. A combined analysis of the two reactions was performed for the first time to investigate the isoscalar character of the 1− states in 90,94Zr. The (p,p′γ) cross section was calculated using values for the isoscalar electric dipole energy-weighted sum rule (E1 ISEWSR) obtained from the (α,α′γ) data. The isoscalar strength for 90Zr was found to exhaust 20 ± 2.5% of the EWSR in the energy range up to 12 MeV. In case of 94Zr, a strength of 9 ± 1.1% of the EWSR was found in the range up to 8.5 MeV.Although an overall general description was obtained in the studied energy intervals, not all proton cross sections were well reproduced using the isoscalar strength from (α,α′γ). This might suggest mixing of isoscalar and isovector components and that this mixing and the degree of collectivity are not the same for all the 1− states below the particle binding energy.

【 授权许可】

Unknown