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High-spin study of 162Ta
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.ORCID iD: 0000-0003-1996-0805
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.ORCID iD: 0000-0003-1771-2656
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
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2011 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 84, no 6, 064312- p.Article in journal (Refereed) Published
Abstract [en]

Excited states in the odd-odd neutron deficient nucleus (162)Ta (Z = 73, N = 89) have been studied for the first time. The gamma spectroscopy analysis using gamma - gamma - gamma coincidences revealed a strongly coupled rotational structure that was established up to large angular momentum states. The rotational band was assigned to the configuration pi h(11/2)[514]9/2 circle times nu i(13/2)[660]1/2 based on its rotational and electromagnetic properties. The data are interpreted within the framework of total Routhian surface calculations, which suggests an axially symmetric shape with a gamma-softminimum at beta(2) approximate to 0.16 and gamma approximate to 6 degrees. The crossing of the signature partners observed in heavier (N >= 91) odd-odd nuclides in this mass region is found to be absent at N = 89. This might be correlated with a change in S-band structure above the paired band crossing at these neutron numbers.

Place, publisher, year, edition, pages
2011. Vol. 84, no 6, 064312- p.
National Category
Subatomic Physics
Research subject
SRA - E-Science (SeRC)
Identifiers
URN: urn:nbn:se:kth:diva-51357DOI: 10.1103/PhysRevC.84.064312ISI: 000298130400001Scopus ID: 2-s2.0-84855366031OAI: oai:DiVA.org:kth-51357DiVA: diva2:463996
Funder
Swedish e‐Science Research Center
Note

QC 20120210

Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2017-12-08Bibliographically approved
In thesis
1. In-Beam Spectroscopy of the Neutron Deficient Nuclei 92Pd and 162Ta
Open this publication in new window or tab >>In-Beam Spectroscopy of the Neutron Deficient Nuclei 92Pd and 162Ta
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Studies of nuclei far from stability offers new insights into the complete nucleon many-body problem. In nuclei with equal neutron and proton numbers (N=Z), the unique nature of the atomic nucleus as an object composed of two distinct types of fermions can be expressed as enhanced correlations arising between neutrons and protons occupying orbitals with the same quantum numbers. Such correlations have since several decades been predicted to favour a new type of nuclear superfluidity; isoscalar neutron-proton pairing, in addition to normal isovector pairing which dominates the structure of most known nuclei. Despite many experimental efforts these predictions have not been confirmed. The N=Z nuclei with mass number A>90 can only be produced in the laboratory at very low cross sections. The related problems of identifying and distinguishing such reaction products and their associated gamma rays from the vast array of N>Z nuclei that are present in much greater numbers have prevented observation of their low-lying excited states until recently. In the present work the experimental difficulties of observation of excited states in the N=Z=46 nucleus 92Pd have been overcome through the use of a highly efficient, state-of-the-art detector system and a prolonged experimental running period. The lowest excited states in 92Pd was empirically observed via detection of gamma rays emitted in the fusion-evaporation reaction together with detection of charged particles and neutrons in the ancillary detector system. The level spacings in the ground state band of 92Pd give the first experimental evidence for a new spin-aligned neutron-proton (np) paired phase. These findings reconcile with nuclear shell model calculations which predicts an unexpected effect of enhanced np correlations for N=Z nuclei in the immediate vicinity of the doubly magic nucleus 100Sn. Excited states of the odd-odd nucleus 162Ta have been observed using the JUROGAM/RITU experimental set-up. This nucleus is located in a transitional region in the nuclide chart which is between near-spherical nuclei and well-deformed nuclei, offering the possibility to study the emergence of collective phenomena and nuclear deformation (in particular the degree of triaxiality). The results, which are interpreted in the framework of the cranked shell model with total Routhian surface calculations suggest an almost axially symmetric nuclear shape. The energy staggering between the signature partners of the yrast rotational bands has been deduced for eight odd-odd isotopes in the neighborhood of 162Ta nucleus and the special observed feature of signature inversion for these nuclei is discussed.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. viii, 48 p.
Series
Trita-FYS, ISSN 0280-316X ; 2011:61
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-50501 (URN)978-91-7501-210-0 (ISBN)
Presentation
2011-12-20, FD5, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:30 (English)
Opponent
Supervisors
Note
QC 20111212Available from: 2011-12-12 Created: 2011-12-06 Last updated: 2011-12-12Bibliographically approved
2. Experimental Nuclear Structure Studies in the Vicinityof the N = Z Nucleus 100Sn and in the ExtremelyNeutron Deficient 162Ta Nucleus
Open this publication in new window or tab >>Experimental Nuclear Structure Studies in the Vicinityof the N = Z Nucleus 100Sn and in the ExtremelyNeutron Deficient 162Ta Nucleus
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work covers spectroscopic studies of nuclei from different regions of the Segré chart whose properties illustrate the delicate balance between the forces in the atomic nucleus. Studies of nuclei far from stability offer new insights into the complex nucleon many-body problem. In nuclei with equal neutron and proton numbers (N = Z), the unique nature of the atomic nucleus as an object composed of two distinct types of fermions can be expressed as enhanced correlations arising between neutrons and protons occupying orbitals with the same quantum numbers. The bound N = Z nuclei with mass number A > 90 can only be produced in the laboratory at very low cross sections. The related problems of identifying and distinguishing such reaction products and their associated gamma rays have prevented a firm interpretation of their structure even for the lowest excited states until recently. In the present work the experimental difficulties of observation of excited states in the N = Z = 46 nucleus 92Pd have been overcome through the use of a highly efficient, state-of-the-art detector system; the EXOGAM-Neutron Wall-DIAMANT setup, and a prolonged experimental running period. The level spacings in the ground state band of 92Pd give the first experimental evidence for a new spin-aligned neutron-proton (np) paired phase, an unexpected effect of enhanced np correlations for N = Z nuclei in the immediate vicinity of the doubly magic nucleus 100Sn.

Excited states in 94Ru and 95Rh nuclei close to the double magic shell  Z = N = 50 have been studied in order to untangle the ambiguity of the spin and the parity of the lowest-lying states. The observed yrast structures are compared to results of large-scale shell model (LSSM) calculations and the strengths of hindered E1 transitions are used as a sensitive test of the LSSM parameters. The effect of single-particle-hole excitations is discussed in terms of the strength of hindered E1 transitions.

Excited states of the odd-odd nucleus 162Ta have been observed using the JUROGAM/RITU experimental set-up. This nucleus is located in a transitional region in the nuclide chart which is between near-spherical nuclei and well-deformed nuclei, offering the possibility to study the emergence of collective phenomena and nuclear deformation (in particular the degree of triaxiality). The results, which are interpreted in the framework of the cranked shell model with total Routhian surface calculations, suggest an almost axially symmetric nuclear shape. The energy staggering between the signature partners of the yrast rotational bands has been deduced for eight odd-odd isotopes in the neighborhood of 162Ta nucleus and the special observed feature of signature inversion for these nuclei is discussed.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. viii, 75 p.
Series
TRITA-FYS, ISSN 0280-316X ; 14:02
Keyword
Nuclear structure
National Category
Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-141421 (URN)978-91-7595-007-5 (ISBN)
Public defence
2014-02-28, FB52, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140217

Available from: 2014-02-14 Created: 2014-02-14 Last updated: 2014-05-16Bibliographically approved

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Bäck, TorbjörnCederwall, BoQi, Chong

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