Heavy Ion Accelerator Facility Department of Nuclear Physics Australian National University

Dracoulis, George

doi:10.1080/10506899909411106

Cited by 6 publications

(6 citation statements)

References 54 publications

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“…The experiment was performed at the Australian National University (ANU) Heavy Ion Accelerator Facility [5] in which excited states in 174 Re were populated via the fusion evaporation reaction 160 Dy( 19 F, 5n) 174 Re. A self-supporting 160 Dy target of thickness 4.2 mg cm −2 , enriched to 79% purity and positioned at an angle of 70 • to the beam, was irradiated by a pulsed beam of 107 MeV 19 F 7+ ions that were produced by the 14 UD Pelletron and delivered to the target position with an average intensity of 1.4 e nA for approximately 100 hours.…”

Section: Methodsmentioning

confidence: 99%

γ -ray spectroscopy of a four-quasiparticle isomer band in Re174

et al. 2020

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Excited states in 174 Re have been populated in fusion-evaporation reactions at the Australian National University, and γ -ray spectroscopy has been used to determine the level structure and to deduce the underlying nucleon configurations. The half-life of the bandhead of the K π = 8 − band has been measured to be 2.7(4) ns. A band built on an isomeric state of spin-parity (14 − ) and a half-life of 53(5) ns has been observed here for the first time, and has been determined to have a four-quasiparticle structure. Contrasting reduced-hindrance values for its decay are discussed in terms of deformation and configuration changes, as indicated by configuration-constrained potential energy surface calculations.

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Section: Methodsmentioning

confidence: 99%

γ -ray spectroscopy of a four-quasiparticle isomer band in Re174

et al. 2020

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“…Sources of 182 Re with activities of between 1 and 3 μCi were created for offline measurement by the irradiation of 1-mg/cm 2 …”

Section: Introductionmentioning

confidence: 99%

“…The current spectrometers available at the ANU-HIAF are the Compton suppressed array (CAESAR) [2] and the Superconducting electron spectrometer (Super-e) [3]. However, neither are suitable for extracting E0 strengths from complex data sets.…”

Section: Introductionmentioning

confidence: 99%

Decay spectroscopy with Solenogam at the ANU Heavy Ion Accelerator Facility

Gerathy¹,

Reed²,

Lane³

et al. 2016

EPJ Web Conf.

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Abstract. Solenogam is a recoil spectrometer designed and constructed for use at the Australian National University (ANU) Heavy-Ion Accelerator Facility (HIAF). The design enables the study of nuclear excitations populated by the decay of long-lived states such as isomers and radioactive ground states. Solenogam is comprised of high-sensitivity γ-ray and electron detector arrays coupled to a new 8-T solenoid. While the installation of the 8-T solenoid proceeds, off-line measurements have been made to characterise Solenogam's performance. Gamma-electron coincidences in the electron capture decay of 182 Re into 182 W were used to investigate conversion coefficients and γ-e − angular correlations. The measured conversion coefficients show good agreement with theoretical calculations and have been used to extract E0/E2 mixing ratios for a number of J → J transitions. The angular correlations measured by the array are in qualitative agreement with theoretical calculations. However, the magnitudes of the correlations are attenuated by approximately 40% for reasons unknown at present. These results are the first full use of the Solenogam system for γ-e − coincidence measurements and have proven that the system is capable of highly-sensitive internal conversion analysis of complex decays.

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“…Pulsed and chopped beams were provided by the 14UD tandem accelerator at the ANU Heavy Ion Accelerator Facility [10] at an energy of 57 MeV. This beam energy provided the greatest cross section for 164 Er production through the 160 Gd( 9 Be,5n) reaction, in concordance with the objective of measuring isomer properties in that nucleus [11].…”

mentioning

confidence: 99%

Discovery of a nonyrastKπ=8+isomer inDy162
Swan
¹
,
Walker
²
,
Podolyák
³

et al. 2011
Phys. Rev. C
10
0
4
0
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The 160 Gd( 9 Be,α3n) 162 Dy reaction has been used to study high-spin states in 162 Dy. Pulsed beam conditions were utilised for enhanced isomer sensitivity. An isomer at 2188.1(3) keV with a half-life of 8.3(3) µs has been discovered and assigned K π = 8 + with a 2-quasineutron configuration. Among eleven γ-ray decay branches, an E2, ∆K= 8 transition to the ground-state band was observed with a reduced hindrance of fν =35, agreeing well with systematics correlating fν with the product of the valence neutron and proton numbers (NpNn) over an extended N, Z range. Small deviations from NpNn dependence are analysed for a range of 2-quasiparticle isomer decays, and interpreted as arising from a weak dependence on the isomer excitation energy relative to the yrast line.PACS numbers: 23.35.+g, 21.10.Ky, 23.20.Lv Understanding the decay rates from high-spin isomers in deformed nuclei remains a considerable challenge [1], and lacks an appropriate theoretical framework. Nevertheless, such isomers, apart from their own structural interest, may be important more generally -in astrophysical environments, at the limits of stability, and controversially, for novel energy storage applications [2]. The present work attempts to clarify the relative importance of some of the degrees of freedom involved in isomer deexcitation.The K quantum number is the projection of the angular momentum on the symmetry axis of the deformed nuclear shape. Half-life measurements for isomer decays that involve a change of K can establish the degree to which K is conserved. The reduced hindrance [1] for the isomeric state (f ν = F 1/ν W ) relates the Weisskopf hindrance factor for the decay (F W = T γ 1/2 /T W 1/2 ) to the K-forbiddenness (ν = ∆K − λ), where T γ 1/2 is the partial gamma half-life, T W 1/2 is the Weisskopf estimate, and λ is the γ-ray multipolarity. This systematic approach to categorising isomer decay rates can be extended by considering variables that reduce K-conservation by generating mixing [3].One form of K-mixing arises due to the Coriolis effect, which intensifies with decreasing neutron and proton number in the lower half of the N = 82 → 126 and Z = 50 → 82 shells due to the population of high-j, low-Ω orbitals. In contrast, greater axial asymmetry occurs with increasing neutron and proton number in the upper half of the shells, leading to an increase in K-mixing associated with γ-tunnelling, where γ is the axial asymmetry parameter. The systematic effect of Coriolis and γ-induced Kmixing may surprisingly be characterised through a single variable, the product of the valence neutron and proton numbers, N p N n , at least for 2-quasiparticle (2QP) iso- * Electronic address: t.swan@surrey.ac.uk mers decaying by E2 transitions [4]. The N p N n product has proven be useful in describing structural changes over extended regions [5]. For higher QP numbers there is a level-density effect that manifests as a dependence on the isomer's excitation energy relative to a rigid rotor (E − E R ), which is correlated with greater K-mixi...

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Heavy Ion Accelerator Facility Department of Nuclear Physics Australian National University

Cited by 6 publications

References 54 publications

γ -ray spectroscopy of a four-quasiparticle isomer band in Re174

γ -ray spectroscopy of a four-quasiparticle isomer band in Re174

Decay spectroscopy with Solenogam at the ANU Heavy Ion Accelerator Facility

Discovery of a nonyrastKπ=8+isomer inDy162
Swan
¹
,
Walker
²
,
Podolyák
³

et al. 2011
Phys. Rev. C
10
0
4
0
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Heavy Ion Accelerator Facility Department of Nuclear Physics Australian National University

Cited by 6 publications

References 54 publications

γ -ray spectroscopy of a four-quasiparticle isomer band in Re174

γ -ray spectroscopy of a four-quasiparticle isomer band in Re174

Decay spectroscopy with Solenogam at the ANU Heavy Ion Accelerator Facility

Discovery of a nonyrastKπ=8+isomer inDy162Swan1, Walker2, Podolyák3 et al. 2011Phys. Rev. C10040View full textAdd to dashboardCite

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Discovery of a nonyrastKπ=8+isomer inDy162
Swan
¹
,
Walker
²
,
Podolyák
³

et al. 2011
Phys. Rev. C
10
0
4
0
View full text Add to dashboard Cite