Nearly complete level scheme of Sn116 below 4.3 MeV

S. Raman, T. A. Walkiewicz, S. Kahane, E. T. Jurney, J. Sa, Z. Gácsi, J. L. Weil, K. Allaart, G. Bonsignori, and J. F. Shriner, Jr.
Phys. Rev. C 43, 521 – Published 1 February 1991
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Abstract

The level scheme of Sn116 has been studied by combining the results of Sn115(n)116Sn and Sn116(n,nγ)116Sn experiments. Both experiments were performed using isotopically enriched samples and Ge γ-ray detectors. Based on the thresholds of γ-ray excitation functions measured for the Sn116(n,nγ) reaction and the precise γ-ray energies from the capture reaction, 100 levels were observed below 4.3 MeV excitation energy. Approximately half of these were not known previously. Forty-eight of these levels have unique or tentative spin-parity assignments, and for ten more the spin has been restricted to a single value. The spin-parity for most other levels below 4.3 MeV excitation has been restricted to a few values. These spin-parity assignments and limitations were derived mainly from (n,nγ) angular distribution measurements, together with additional information obtained from the cross section magnitudes in both experiments.

Above 4.3 MeV excitation energy, 55 additional levels are proposed, based only on the Sn115(n,γ) results. No Jπ information is available for these higher-lying levels beyond the fact that they most probably all have J≤4. The level scheme below 4.3 MeV from the current work, together with known high-spin levels up to 5.4 MeV seen in other experiments, are compared to the combined predictions of the two-broken-pair model, the interacting boson model, and the deformed collective model. In addition, several states have been phenomenologically identified as proton 1p-1h and collective quadrupole-octupole two-phonon excitations. It is concluded from the good agreement between experiment and these models that all levels in Sn116 with J≤6 up to an excitation of 4.0 MeV and J≤3 up to 4.3 MeV may have been experimentally identified. The nearest-neighbor spacing distribution is intermediate between that of a Gaussian orthogonal ensemble and that of a Poisson distribution, with a slight preference for the former. The neutron separation energy was determined to be 9563.47±0.11 keV.

  • Received 15 October 1990

DOI:https://doi.org/10.1103/PhysRevC.43.521

©1991 American Physical Society

Authors & Affiliations

S. Raman, T. A. Walkiewicz, and S. Kahane

  • Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831

E. T. Jurney

  • Los Alamos National Laboratory, Los Alamos, New Mexico 87545

J. Sa, Z. Gácsi, and J. L. Weil

  • University of Kentucky, Lexington, Kentucky, 40506

K. Allaart

  • Faculty of Physics and Astronomy, Free University, Amsterdam, The Netherlands

G. Bonsignori

  • Dipartimento di Fisica dell’Universita Bologna, Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Italy

J. F. Shriner, Jr.

  • Tennessee Technological University, Cookeville, Tennessee 38505

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Issue

Vol. 43, Iss. 2 — February 1991

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