Projects per year
Abstract
Background: The nuclear shape is a macroscopic feature of an atomic nucleus that is sensitive to the underlying nuclear structure in terms of collectivity and the interaction between nucleons. Therefore, the evolution of nuclear shapes has attracted many theoretical and experimental nuclear structure studies. The structure of the A≈70, N≈Z nuclei, lying far from the stability line, is interesting because a particularly strong proton-neutron correlation may occur here due to the occupation of the same orbits by nucleons of both types. In this region, different particle configurations drive a nucleus towards various deformed shapes: prolate, oblate, octupole, or nonaxial. These nuclear shapes change rapidly with nucleon number and also with angular momentum. This is reflected by a presence of different structures (bands) of excited states which exhibit a broad range of lifetimes. Purpose: The aim of this paper is to determine lifetimes of some high-spin excited states in As69 and Ge66 nuclei to examine the shape evolution in these neutron-deficient nuclei. Methods: Lifetimes of high-spin states in As69 and Ge66 have been measured by using the Doppler-shift attenuation technique with the GASP and recoil filter detector setup at the Laboratori Nazionali di Legnaro. The nuclei of interest were produced in the S32(95MeV)+0.8mg/cm2 Ca40 fusion-evaporation reaction. The strongest reaction channels 3p and α2p led to the As69 and Ge66 final nuclei, respectively. Using γ-γ-recoil coincidences we were able to determine very short lifetimes (in the femtosecond range) in the residual nuclei of interest. Results: In As69, the extracted lifetimes are τ=72 (-32, +45) fs for the 33/2+ state at 7897 keV and τ<85 fs for the 37/2+ state at 9820 keV. For the Ge66 case, the lifetime of the 11- state at 7130 keV is τ=122(±41) fs. Lifetimes in As69 and Ge66 reported in this paper have been measured for the first time in the present experiment. Conclusions: The results are discussed in the terms of deformation and shape evolution in As69 and Ge66. The quadrupole moments deduced from the measured lifetimes were compared with the cranked Woods-Saxon-Strutinsky calculations by means of the total Routhian surface method. It turns out that Band 3 in As69 shows an oblate-prolate shape transition, and above spin 33/2+ it corresponds to a prolate collective structure with β2≈0.27 and γ≈20. In turn, in Ge66 the negative-parity band built on the 7- state at 4205 keV corresponds to a triaxial shape with β2=0.33 and γ=31. Analysis of the transitional quadrupole moments derived from the experimental and theoretical ones points to a significant change of deformation in the As69 and Ge66 nuclei with increasing rotational frequency.
| Original language | English |
|---|---|
| Article number | 054330 |
| Journal | Physical Review C |
| Volume | 100 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 26 Nov 2019 |
Bibliographical note
©2019 American Physical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.Projects
- 2 Finished
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Nuclear Physics Consolidated Grant
Jenkins, D. (Principal investigator), Andreyev, A. (Co-investigator), Bentley, M. (Co-investigator), Diget, C. A. (Co-investigator), Dobaczewski, J. J. (Co-investigator), Fulton, B. R. (Co-investigator), Laird, A. M. (Co-investigator), Paschalis, S. (Co-investigator), Pastore, A. (Co-investigator), Petri, M. (Co-investigator) & Wadsworth, R. (Co-investigator)
SCIENCE AND TECHNOLOGY FACILITIES COUNCIL (STFC)
1/10/17 → 30/09/22
Project: Research project (funded) › Research
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Nuclear Physics Consolidated Grant
Wadsworth, R. (Principal investigator), Wadsworth, R. (Principal investigator), Andreyev, A. (Co-investigator), Andreyev, A. (Co-investigator), Barton, C. J. (Co-investigator), Diget, C. A. (Co-investigator), Diget, C. A. (Co-investigator), Fulton, B. R. (Co-investigator), Fulton, B. R. (Co-investigator), Jenkins, D. (Co-investigator), Jenkins, D. (Co-investigator), Laird, A. M. (Co-investigator) & Laird, A. M. (Co-investigator)
SCIENCE AND TECHNOLOGY FACILITIES COUNCIL (STFC)
1/08/14 → 30/09/18
Project: Research project (funded) › Research