ISHII Tetsuro Japan Atomic Energy Agency

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In-beam g -ray spectroscopy of neutron-rich nuclei in the uranium region through the heavy-ion transfer reaction. JAEA H. Makii, M. Asai, H. Koura, K. Tsukada, A. Toyoshima, M. Matsuda, T. Shizuma, S. Ichikawa Tokyo Institute of Technology S. Shigematsu, T. Kohno - PowerPoint PPT Presentation

Text of ISHII Tetsuro Japan Atomic Energy Agency

  • In-beam g-ray spectroscopy of neutron-rich nuclei in the uranium region through the heavy-ion transfer reaction ISHII TetsuroJapan Atomic Energy AgencyJAEA H. Makii, M. Asai, H. Koura, K. Tsukada, A. Toyoshima, M. Matsuda, T. Shizuma, S. IchikawaTokyo Institute of Technology S. Shigematsu, T. KohnoNational Defense Medical Colledge A. MakishimaKomazawa Univ. J. Kaneko, M. OgawaOsaka Univ. I. Hossain, Ibaraki Univ. H. Toume JAEA-Tokai Tandem Accelerator

  • Where are deformed / spherical shell gaps ? high-L (k17/2) orbitals ? In-beam g-ray spectroscopy using heavy-ion transfer reactions - 238U,244Pu,248Cm targets; (18O,16O), (18O, 20Ne) selection of reaction channels using Si DE-E First g-ray measurements of 236Th, 240,242U, 246Pu, 250Cm - establishment of ground-state bands up to 12+ states Systematics of E(21+) in the neutron-rich U region - disappearance of N=152 deformed shell gap at 94Pu - possibility of the spherical shell gap at N=164 for 256U164

    Nuclear structure at the largest neutron number

  • b-stability More Neutron-rich than the b-stability 294110Ds184T1/2 ~300y

  • 18O beam 162 MeV(18MV) @Tokai-Tandem248Cm target (0.8mg/cm2) f3mm, 45kBq 4 Si DE-E telescopesDE: 75mm thickness6 Ge detectors Seff = 12% @ 0.2 MeV 3% @ 1.3 MeVExperimental setup

  • ONCBBeFSi E-DE PLOT248Cm(18O,16O)250Cm; 2neutron-strippingDEAZ2/E E-DE Plots & g-ray spectra of 250Cm154 s~0.5mb

  • 248Cm(18O,16O)250Cm; 2neutron-strippingComplete selection of g-rays in residual nuclei by measuring outgoing particles - Z, A, and kinetic energies - Si E-DE PLOTgateEx of 250Cm < Sn E-DE Plots & g-ray spectra of 250Cm154

  • Level schemes of 240U, 246Pu and 250Cm by (18O,16O)

  • Level Schemes of 236Th and 242U by (18O,20Ne)

  • Five new dataExperimentCalculationSobiczewski et al., PRC 63(2001)034306Moments of inertia and N=152 deformed shell

  • Narrower energy gap at N=152 for 94PuExperiment245Pu1511/2[620]9/2[734]present in-beam g-ray data combined with the (d,p) data at ANL in 70s

  • Possibility of spherical shell closure of N=164 in the U regionpairing energy gap (D) moment of inertia (E2+ ) 25692U164 is sphericalMinimumDeformed shell gap N=126

  • S.P.E. calculated by Koura-Yamada potential (modified Woods-Saxon)

  • Summary

    First measurements of deexcitaion g-rays in 5 neutron-rich nuclei in the U region (18O, 16O) 2n-strippping; 240U, 246Pu and 250Cm up to 12+ s~0.5mb (18O, 20Ne) 2p-pickup ; 236Th and 242U up to 10+ and 8+ s~mb - complete selection of g-rays by Z and M by measuring the outgoing particles with Si DE-E 250Cm154 : first in-beam g-ray study beyond N=152

    Disappearance of N=152 deformed shell gap for 94Pu - from the systematics of the E(21+) energies and from the single particle levels in 245Pu151

    Possibility of the spherical shell closure of N=164 - supported by the calculation using the Koura-Yamada potential240U: T. Ishii et al., Phys. Rev. C 72 (2005) 021301(R)250Cm: T. Ishii et al., J. Phys. Soc. Jpn. 75 (2006) 043201

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