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Phys. Rev. C 75, 034311 (2007) [18 pages]

Transition strengths and degree of deformation in 79Sr

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R. A. Kaye1,2, Y. K. Ryu1, S. R. Arora1,*, S. L. Tabor2, J. Döring3,†, Y. Sun4,5, T. D. Baldwin2,‡, D. B. Campbell2,§, C. Chandler2,**, M. W. Cooper2,††, S. M. Gerbick2,6,‡‡, O. Grubor-Urosevic6, C. R. Hoffman2, J. Pavan2,a, L. A. Riley7,b, and M. Wiedeking2,a
1Department of Physics and Astronomy, Ohio Wesleyan University, Delaware, Ohio 43015, USA
2Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
3Gesellschaft für Schwerionenforschung (GSI), Planckstr. 1, D-64291 Darmstadt, Germany
4Department of Physics and Joint Institute of Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46556, USA
5Department of Physics, Xuzhou Normal University, Xuzhou, Jiangsu 221009, People's Republic of China
6Department of Chemistry and Physics, Purdue University Calumet, Hammond, Indiana 46323, USA
7Department of Physics and Astronomy, Earlham College, Richmond, Indiana 47374, USA

Received 27 November 2006; published 22 March 2007

High-spin states in 79Sr were studied using the 54Fe(28Si,2pn) reaction at 90 MeV, with a thick 14-mg/cm2 54Fe target used to stop all recoils. Prompt γ-γ coincidences were detected using the Florida State University Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. The most recent 79Sr level scheme has been confirmed in three separate band structures up to a spin as high as the (37/2+) yrast state based on γ-ray coincidence relations, intensity and effective lifetime measurements, and directional correlation of oriented nuclei ratios. Lifetimes of 33 excited states were measured using the Doppler-shift attenuation method, with the experimental line shapes obtained at two separate observation angles and by gating from above the transitions of interest whenever possible. Transition quadrupole moments Qt inferred from the lifetimes indicate a high degree of collectivity and deformation over a rather wide range of spins in all three observed bands, with evidence for modest reductions in the values with increasing spin. The changes in Qt are attributed to the onset of quasiproton alignment and are supported qualitatively by the predictions of the projected shell model and cranked Woods-Saxon calculations in conjunction with the cranked shell model. Lifetimes measured in a band based on the [431]1/2+ intrinsic Nilsson configuration suggest a large quadrupole deformation (β2≈0.41) associated with this band, providing another example of the strong deformation-driving properties of the d5/2 intruder orbital in the mass 80 region.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevC.75.034311
DOI:
10.1103/PhysRevC.75.034311
PACS:
21.10.Tg, 23.20.Lv, 27.50.+e

*Present address: Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA.

†Present address: Bundesamt für Strahlenschutz, D-10318 Berlin, Germany.

‡Present address: Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.

§Present address: Lawrence Livermore National Laboratory, Livermore, California 94551, USA.

**Present address: School of Chemistry and Physics, Keele University, Keele, Staffordshire, ST5 5BG, United Kingdom.

††Present address: Pacific Northwest National Laboratory, Richland, Washington 99352, USA.

‡‡Present address: Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.

aPresent address: Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

bPresent address: Department of Physics and Astronomy, Ursinus College, Collegeville, Pennsylvania 19426, USA.

 
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