Nuclear Levels in Re188

E. B. Shera, U. Gruber, B. P. K. Maier, H. R. Koch, O. W. B. Schult, R. G. Lanier, N. Onishi, and R. K. Sheline
Phys. Rev. C 6, 537 – Published 1 August 1972
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Abstract

Nuclear levels in Re188 have been investigated using the following experimental techniques: measurement of neutron-capture γ-ray transitions with energies between 4.8 and 6.0 MeV using a Ge(Li) pair spectrometer; study of (d,p) spectra using 12-MeV deuterons and a broad-range magnetic spectrograph; measurement of (n,γ) spectra between 45 and 830 keV with a bent-crystal spectrometer; coincidence studies of the (n,γ) radiation using two Ge(Li) detectors, including a study of short-lived isomeric states using delayed-coincidence techniques; and observation of the γ rays following β decay of W188 using a Ge(Li) detector. A nuclear level scheme for Re188 has been constructed by combining the results of the above measurements with published data. Information, including spin and parity assignments, is presented on 36 low-lying levels. The lifetimes of five excited states are reported. The Nilsson model has been used to interpret the level structure. Assignments are proposed which involve 15 separate rotational bands. Proposed Nilsson configurations, band-head energies, and band-head lifetimes (if known) are: 1[402↑ - 512↓], 0.0 keV; 3[402↑ + 510↑], 169.4 keV; 6[402↑ + 503↑], 172.1 keV, 19 min; 4[402↑ + 512↑], 182.7 keV, 18 nsec; 2[402↑ - 505↓], 205.3 keV, 3.2 nsec; 0+[514↑ - 505↓], 207.9 keV, 3.2 nsec; 3+[514↑ - 512↓], 230.9 keV, 21 nsec; 2[402↑ - 510↑], 256.9 keV; 1[402↑ + 503↑], 290.7 keV; 4[402↑ + 501↑], 325.9 keV; 5+[514↑ + 510↑], 360.9 keV, 5.2 nsec; 3+[402↑ - 615↑], 439.7 keV; 1+[514↑ - 503↑], 482.2 keV; 1[402↑ - 501↑], 556.8 keV. A Kπ=1 band, believed to be predominantly a |K2| γ-vibrational band, is observed at 582.2 keV. The measured (d,p) reaction cross sections are compared with theoretical calculations based on these assignments. The β-decay measurements have revealed a previously unknown β branch from the W188 ground state to a Iπ=0+ level at 207.9 keV. This 0+0+ transition (logft=9.9) is discussed in terms of isobaric analog state mixing. Results of a calculation which uses a parametrized residual neutron-proton interaction to predict the parallel-antiparallel splitting energies and K=0 even-odd shifts in Re186 and Re188 are presented and compared with experiment.

  • Received 24 April 1972

DOI:https://doi.org/10.1103/PhysRevC.6.537

©1972 American Physical Society

Authors & Affiliations

E. B. Shera

  • University of California, Los Alamos Scientific Laboratory, Los Alamos, New Mexico 87544

U. Gruber, B. P. K. Maier, H. R. Koch, and O. W. B. Schult

  • Technical University, Munich, Germany
  • Research Establishment of The Danish Atomic Energy Commission, Risø, Roskilde, Denmark

R. G. Lanier

  • University of California, Lawrence Livermore Laboratory, Livermore, California 94550

N. Onishi and R. K. Sheline

  • Florida State University, Tallahassee, Florida 32304

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Vol. 6, Iss. 2 — August 1972

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