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Ideguchi E, Kibédi T, Dowie JTH, Hoang TH, Kumar Raju M, Aoi N, Mitchell AJ, Stuchbery AE, Shimizu N, Utsuno Y, Akber A, Bignell LJ, Coombes BJ, Eriksen TK, Gray TJ, Lane GJ, McCormick BP. Electric Monopole Transition from the Superdeformed Band in ^{40}Ca. PHYSICAL REVIEW LETTERS 2022; 128:252501. [PMID: 35802446 DOI: 10.1103/physrevlett.128.252501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 01/31/2022] [Accepted: 04/20/2022] [Indexed: 06/15/2023]
Abstract
The electric monopole (E0) transition strength ρ^{2} for the transition connecting the third 0^{+} level, a "superdeformed" band head, to the "spherical" 0^{+} ground state in doubly magic ^{40}Ca is determined via e^{+}e^{-} pair-conversion spectroscopy. The measured value ρ^{2}(E0;0_{3}^{+}→0_{1}^{+})=2.3(5)×10^{-3} is the smallest ρ^{2}(E0;0^{+}→0^{+}) found in A<50 nuclei. In contrast, the E0 transition strength to the ground state observed from the second 0^{+} state, a band head of "normal" deformation, is an order of magnitude larger ρ^{2}(E0;0_{2}^{+}→0_{1}^{+})=25.9(16)×10^{-3}, which shows significant mixing between these two states. Large-scale shell-model (LSSM) calculations are performed to understand the microscopic structure of the excited states and the configuration mixing between them; experimental ρ^{2} values in ^{40}Ca and neighboring isotopes are well reproduced by the LSSM calculations. The unusually small ρ^{2}(E0;0_{3}^{+}→0_{1}^{+}) value is due to destructive interference in the mixing of shape-coexisting structures, which are based on several different multiparticle-multihole excitations. This observation goes beyond the usual treatment of E0 strengths, where two-state shape mixing cannot result in destructive interference.
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Affiliation(s)
- E Ideguchi
- Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - T Kibédi
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - J T H Dowie
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - T H Hoang
- Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - M Kumar Raju
- Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
- Department of Physics, GITAM Institute of Science, GITAM University, Visakhapatnam-530045, India
| | - N Aoi
- Research Center for Nuclear Physics (RCNP), Osaka University, 10-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - A J Mitchell
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - A E Stuchbery
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - N Shimizu
- Center for Nuclear Study, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Y Utsuno
- Center for Nuclear Study, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - A Akber
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - L J Bignell
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - B J Coombes
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - T K Eriksen
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - T J Gray
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - G J Lane
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
| | - B P McCormick
- Department of Nuclear Physics and Accelerator Applications, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
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