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Träfflista för sökning "WFRF:(Sandzelius M.) "

Sökning: WFRF:(Sandzelius M.)

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1.
  • Ertoprak, Aysegul, et al. (författare)
  • Evidence for octupole collectivity in 172Pt
  • 2020
  • Ingår i: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 56:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the extremely neutron-deficient nucleus 172Pt were populated via 96Ru(78Kr,2p) and 92Mo(83Kr,3n) reactions. The level scheme has been extended up to an excitation energy of  ~ 5 MeV and tentative spin-parity assignments up to Iπ = 18+. Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negative-parity band. The lowest member of this negative-parity structure was firmly assigned spin-parity 3-. In addition, we observed an E3 transition from this 3- state to the ground state, providing direct evidence for octupole collectivity in 172Pt. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3- state as a collective octupole-vibrational state.
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2.
  • Parr, E., et al. (författare)
  • Single-particle states and parity doublets in odd- Z Ac 221 and Pa 225 from α -decay spectroscopy
  • 2022
  • Ingår i: Physical Review C. - 2469-9985. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Low-lying states in the odd-Z isotopes Ac13289221 and Pa13491225 have been studied using α-particle and αγ-coincidence spectroscopy in the Pa225→Ac221→Fr217 decay chain. Ground-state spin and parity assignments of Iπ = 5/2- are proposed for both Ac221 and Pa225, with the odd proton occupying the ω = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In Ac221, excited states in the bands based on the ω = 5/2 and ω = 3/2 orbitals have been identified, including proposed parity-doublet states. The results suggest that reflection-asymmetric deformation of the ground state persists in the odd-A members of the isotope chains down to N = 132 for Ac and N = 134 for Pa, before reaching the transitional region at N = 130.
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3.
  • Saygi, B., et al. (författare)
  • Reduced transition probabilities along the yrast line in W-166
  • 2017
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 96:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of excited states in the yrast band of the neutron-deficient nuclide W-166 have been measured utilizing the DPUNS plunger device at the target position of the JUROGAM II gamma-ray spectrometer in conjunction with the RITU gas-filled separator and the GREAT focal-plane spectrometer. Excited states in W-166 were populated in the Mo-92(Kr-78, 4p) reaction at a bombarding energy of 380 MeV. The measurements reveal a low value for the ratio of reduced transitions probabilities for the lowest-lying transitions B(E2; 4(+)-> 2(+)) / B(E2; 2(+)-> 0(+)) = 0.33(5), compared with the expected ratio for an axially deformed rotor (B-4/2 = 1.43).
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4.
  • Procter, M. G., et al. (författare)
  • Anomalous transition strength in the proton-unbound nucleus (109)(53)I56
  • 2011
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:3, s. 118-122
  • Tidskriftsartikel (refereegranskat)abstract
    • A lifetime measurement has been made for the first excited 11/2(+) state in the proton-unbound nucleus (109)(53)I56 using the recoil-distance Doppler-shift method in conjunction with recoil-proton tagging. The experimental reduced transition probability is considerably smaller than the prediction of theoretical shell-model calculations using the CD-Bonn nucleon-nucleon potential. The discrepancy between the theoretical and experimental reduced transition strengths in this work most likely arises from the inability of the current shell-model calculations to accurately account for the behavior of the unbound nuclear states.
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5.
  • Procter, M. G., et al. (författare)
  • Lifetime measurement in the proton-unbound nucleus 109I
  • 2011
  • Ingår i: AIP Conf. Proc.. - : AIP. - 9780735409835 ; , s. 105-110
  • Konferensbidrag (refereegranskat)abstract
    • The Recoil-Distance Doppler-shift method has been combined with Recoil-Decay Tagging for the first time to measure a lifetime in the proton-unbound nucleus 109I. The lifetime value was determined using the Differential Decay-Curve method in singles mode. The result has been compared to theoretical shell-model calculations in order to better understand the nature of unbound valence nucleons at the proton drip line.
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6.
  • Cederwall, Bo, 1964-, et al. (författare)
  • Lifetime Measurements of Excited States in Pt-172 and the Variation of Quadrupole Transition Strength with Angular Momentum
  • 2018
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 121:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of the first excited 2(+) and 4(+) states in the extremely neutron -deficient nuclide Pt-172 have been measured for the first time using the recoil-distance Doppler shift and recoil-decay tagging techniques. An unusually low value of the ratio B(E2: 4(1)(+) -> 2(1)(+)/B(E2: 2(1)(+) -> 0(gs)(+)) = 0.55(19) was found, similar to a handful of other such anomalous cases observed in the entire Segre chart. The observation adds to a cluster of a few extremely neutron -deficient nuclides of the heavy transition metals with neutron numbers N approximate to 90-94 featuring the effect. No theoretical model calculations reported to date have been able to explain the anomalously low B(E2: 4(1)(+) -> 2(1)(+)/B(E2: 2(1)(+) -> 0(gs)(+)) ratios observed in these cases. Such low values cannot, e.g., be explained within the framework of the geometrical collective model or by algebraic approaches within the interacting boson model framework. It is proposed that the group of B(E2: 4(1)(+) -> 2(1)(+)/B(E2: 2(1)(+) -> 0(gs)(+)) ratios in the extremely neutron-deficient even-even W, Os, and Pt nuclei around neutron numbers N approximate to 90-94 reveal a quantum phase transition from a seniority-conserving structure to a collective regime as a function of neutron number. Although a system governed by seniority symmetry is the only theoretical framework for which such an effect may naturally occur, the phenomenon is highly unexpected for these nuclei that are not situated near closed shells.
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7.
  • Zhang, W., et al. (författare)
  • Decay spectroscopy of 171,172Os and 171,172,174Ir
  • 2023
  • Ingår i: Physical Review C. - : American Physical Society (APS). - 2469-9985 .- 2469-9993. ; 107:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a study of the α-decay fine structure and the associated Eα−Eγ correlations in the decays of 171,172Os and 171,172,174Ir. In total, 13 new α-decay energy lines have been resolved, and three new γ-ray transitions have been observed following the new decay branches to 168Re and 167W. The weak α-decay branch from the bandhead of the νi13/2 band in 171Os observed in this work highlights an unusual competition between α, β, and electromagnetic decays from this isomeric state. The nucleus 171Os is therefore one of few nuclei observed to exhibit three different decay modes from the same excited state. The nuclei of interest were produced in 92Mo(83Kr,xpyn) fusion-evaporation reactions at the Accelerator Laboratory of the University of Jyväskylä, Finland. The fusion products were selected using the gas-filled ion separator RITU and their decays were characterized using an array of detectors for charged particles and electromagnetic radiation known as GREAT. Prompt γ-ray transitions were detected and correlated with the decays using the JUROGAM II germanium detector array surrounding the target position. Results obtained from total Routhian surface (TRS) calculations suggest that α-decay fine structure and the associated hindrance factors may be a sensitive probe of even relatively small shape changes between the final states in the daughter nucleus.
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8.
  • Bianco, L., et al. (författare)
  • Discovery of W-157 and Os-161
  • 2010
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 690:1, s. 15-18
  • Tidskriftsartikel (refereegranskat)abstract
    • The nuclides W-157 and Os-161 have been discovered ill reactions of Ni-58 ion beams with a Cd-106 target. The Os-161 alpha-decay energy and half-life were 6890 +/- 12 keV and 640 +/- 60 mu s. The daughter W-157 nuclei beta-decayed with a half-life of 275 +/- 40 ms, populating both low-lying alpha-decaying states in Ta-157, which is consistent with a 7/2(-) ground state in W-157. Fine structure observed in the alpha decay of Os-161 places the lowest excited state in W-157 with 1(pi) = 9/2(-) at 318 +/- 30 key. The branching ratio of 5.5(-2.2)(+3.1)% indicates that Os-161 also has a 7/2(-) ground state. Shell-model calculations analysing the effects of monopole shifts and a tensor force on the relative energies of 2f(7/2) and 1h(9/2) neutron states in N = 83 isotones are presented. (C) 2010 Elsevier B.V. All rights reserved.
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9.
  • Hilton, J., et al. (författare)
  • α -spectroscopy studies of the new nuclides Pt 165 and Hg 170
  • 2019
  • Ingår i: Physical Review C. - 2469-9985. ; 100:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The new nuclides Pt165 and Hg170 were produced in the reactions Mo92(Kr78,5n) and Ru96(Kr78,4n) at bombarding energies of 418 MeV and 390 MeV, respectively. For Hg170 an α-particle energy of Eα=7590(30)keV and half-life of t1/2=0.08-0.04+0.40ms were deduced, while for Pt165 the corresponding values were 7272(14) keV and 0.26-0.09+0.26ms. Comparison of the reduced α-decay widths with systematics indicates that both α decays are unhindered. Although combining the measured α-decay Q values with extrapolated masses suggests that both new nuclides are unbound to two-proton emission by more than 1 MeV, their α-decay half-lives are too short for this decay mode to compete. Improved data were also obtained for Pt166,167, produced via the Ru96(Kr78,α4n) and Ru96(Kr78,α3n) reactions at bombarding energies of 390 MeV and 418 MeV.
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10.
  • Joss, D. T., et al. (författare)
  • Evolving collective structures in the transitional nuclei W-162 and W-164
  • 2016
  • Ingår i: PHYSICAL REVIEW C. - : American Physical Society. - 2469-9985. ; 93:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the neutron-deficient nuclides(74)(162)W(88) and W-164(74)90 were investigated by using the gamma-ray spectrometer Jurogam. A change in structure is apparent from the first rotational alignments in W-162 and W-164, whose rotationally aligned bands are interpreted as nu(h(9/2))(2) and nu(i(13/2))(2) configurations, respectively. The level schemes have been extended using recoil (-decay) correlations with the observation of excited collective structures. Configuration assignments have been made on the basis of comparisons of the deduced aligned angular momentum, as a function of rotational frequency, with the predictions of the cranked shell model.
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11.
  • Joss, D. T., et al. (författare)
  • The influence of quasineutron configurations on 161Ta and nearby odd-A nuclei
  • 2011
  • Ingår i: AIP Conf. Proc.. - : AIP. - 9780735409835 ; , s. 43-48
  • Konferensbidrag (refereegranskat)abstract
    • Several strongly coupled bands in the neutron-deficient nucleus 161Ta have been identified and quasiparticle configuration assignments have been made on the basis of rotational alignments and cranked shell model calculations. The level scheme elucidated for 161Ta highlights the competition between the ν(h 9/2) and ν(i 13/2) orbitals to form the yrast spectrum. The band structures in 161Ta also provide new insights into the structural features of other heavy odd-A nuclei populated with much lower reaction cross sections in this region at the proton drip line.
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12.
  • Zhang, Wei, et al. (författare)
  • Lifetime measurements of excited states in 169,171,173Os : Persistence of anomalous B(E2) ratios in transitional rare earth nuclei in the presence of a decoupled i13/2 valence neutron
  • 2021
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 820
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of low-lying excited states in the νi13/2+ bands of the neutron-deficient osmium isotopes 169,171,173Os have been measured for the first time using the recoil-distance Doppler shift and recoil-isomer tagging techniques. An unusually low value is observed for the ratio B(E2;21/2+→17/2+)/B(E2;17/2+→13/2+) in 169Os, similar to the “anomalously” low values of the ratio B(E2;41+→21+)/B(E2;21+→0gs+) previously observed in several transitional rare-earth nuclides with even numbers of neutrons and protons, including the neighbouring 168,170Os. Furthermore, the evolution of B(E2;21/2+→17/2+)/B(E2;17/2+→13/2+) with increasing neutron number in the odd-mass isotopic chain 169,171,173Os is observed to follow the same trend as observed previously in the even-even Os isotopes. These findings indicate that the possible quantum phase transition from a seniority conserving structure to a collective regime as a function of neutron number suggested for the even-even systems is maintained in these odd-mass osmium nuclei, with the odd valence neutron merely acting as a “spectator”. As for the even-even nuclei, the phenomenon is highly unexpected for nuclei that are not situated near closed shells.
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13.
  • Bäck, Torbjörn, et al. (författare)
  • Lifetime measurement of the first excited 2(+) state in (108)Te
  • 2011
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 84:4, s. 041306-
  • Tidskriftsartikel (refereegranskat)abstract
    • The lifetime of the first excited 2(+) state in the neutron deficient nuclide (108)Te has been measured for the first time, using a combined recoil decay tagging and recoil distance Doppler shift technique. The deduced reduced transition probability is B(E2;0(g.s.)(+) -> 2(+)) = 0.39(-0.04)(+0.05)e(2)b(2). Compared to previous experimental data on neutron deficient tellurium isotopes, the new data point constitutes a large step (six neutrons) toward the N = 50 shell closure. In contrast to what has earlier been reported for the light tin isotopes, our result for tellurium does not show any enhanced transition probability with respect to the theoretical predictions and the tellurium systematics including the new data is successfully reproduced by state-of-the-art shell model calculations.
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14.
  • Davis-Merry, T. R., et al. (författare)
  • Collective excitations in the transitional nuclei Re-163 and Re-165
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 91:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the neutron-deficient nuclei (163)(75) Re-88 and (165)(75) Re-90 were populated in the Cd-106(Ni-60, p2n gamma) and Mo-92(Kr-78, 3p2n gamma) fusion-evaporation reactions at bombarding energies of 270 and 380 MeV, respectively.. rays were detected at the target position using the JUROGAM spectrometer while recoiling ions were separated in-flight by the RITU gas-filled recoil separator and implanted in the GREAT spectrometer. The energy level schemes for Re-163 and Re-165 were identified using recoil-decay correlation techniques. At low spin, the yrast bands of these isotopes consist of signature partner bands based on a single pi h(11/2) quasiproton configuration. The bands display large energy splitting consistent with the soft triaxial shape typical of transitional nuclei above N = 82. The configurations of the excited states are proposed within the framework of the cranked shell model.
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15.
  • Drummond, M. C., et al. (författare)
  • Low-lying excited states in the neutron-deficient isotopes Os-163 and Os-165
  • 2013
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:5, s. 054309-
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the neutron-deficient isotopes Os-163 and Os-165 were identified using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator. The Os-163 and Os-165 nuclei were populated via the Cd-106(Ni-60,3n) and Mo-92(Kr-78,2p3n) reactions at bombarding energies of 270 MeV and 357 MeV, respectively. Gamma-ray emissions from these nuclei have been established unambiguously using the recoil-decay tagging technique and a coincidence analysis has allowed level schemes to be established. These results suggest that the yrast states are based upon negative-parity configurations originating from the f(7/2) and h(9/2) orbitals.
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16.
  • Ertoprak, Aysegul, et al. (författare)
  • LIFETIME MEASUREMENTS WITH THE DOPPLER SHIFT ATTENUATION METHOD USING A THICK HOMOGENEOUS PRODUCTION TARGET - VERIFICATION OF THE METHOD
  • 2017
  • Ingår i: Acta Physica Polonica B. - : Jagiellonian University Press. - 0587-4254 .- 1509-5770. ; 48:3, s. 325-329
  • Tidskriftsartikel (refereegranskat)abstract
    • Doppler Shift Attenuation Method (DSAM) analysis of excited-state lifetimes normally employs thin production targets mounted on a thick stopper foil ("backing") serving to slow down and stop the recoiling nuclei of interest in a well-defined manner. Use of a thick, homogeneous production target leads to a more complex analysis as it results in a substantial decrease in the energy of the incident projectile which traverses the target with an associated change in the production cross section of the residues as a function of penetration depth. Here, a DSAM lifetime analysis using a thick homogeneous target has been verified using the Doppler broadened lineshapes of gamma rays following the decay of highly excited states in the semi-magic (N = 50) nucleus Ru-94. Lifetimes of excited states in the Ru-94 nucleus have been obtained using a modified version of the LINESHAPE package from the Doppler broadened lineshapes resulting from the emission of the gamma rays, while the residual nuclei were slowing down in the thick (6 mg/cm(2)) metallic Ni-58 target. The results have been validated by comparison with a previous measurement using a different (RDDS) technique.
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17.
  • Ertoprak, A., et al. (författare)
  • Lifetimes of core-excited states in semi-magic Rh-95
  • 2020
  • Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 56:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of negative-parity states have been determined in the neutron deficient semi-magic (N = 50) nucleus Rh-95. The fusion-evaporation reaction Ni-58(Ca-40, 3p) was used to populate high-spin states in Rh-95 at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator facility. The results were obtained using the Doppler Shift Attenuation Method (DSAM) based on the Doppler broadened line shapes produced during the slowing down process of the residual nuclei in a thick 6 mg/cm(2) metallic target. B(M1) and B(E2) reduced transition strengths are compared with predictions from large-scale shell-model calculations. state-of-the-art theory. Remarkably, the structural features up to moderate angular momentum of nuclei immediately below the N = Z = 50 shell closures can be described with high accuracy in a very simple way by shell-model calculations including only the g(9/2) and p(1/2) subshells. Of special interest is the neutron-proton pair coupling scheme which is expected to appear in the heaviest N=Z nuclei [1,2] and the seniority structure of the N = 50 isotones [3-7]. However, multiple core-excited states have been observed in the semi-magic nuclei of the Sn-100 region [8-10]. The theoretical study of those states is a challenging task, which requires a significantly larger model space for their interpretation. Transition probabilities between nuclear states provide important constraints for theoretical modelling of the structure of the nuclei of interest. Our previous lifetime study of the semimagic (N = 50) nucleus Ru-94 [ 11,12] provided information on the electromagnetic decay properties of neutron-core excited states. We now address lifetime measurements in its closest, more neutron deficient, isotone Rh-95 using the same DSAM technique. The experimental results have been interpreted within the framework of large-scale shell-model (LSSM) calculations.
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18.
  • Ertoprak, Aysegul, 1987-, et al. (författare)
  • M1 and E2 transition rates from core-excited states in semi-magic 94Ru
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Lifetimes of high-spin states have been measured in the semi-magic (N=50) nucleus 94Ru. Excited states in 94Ru were populated in the 58Ni(40Ca, 4p)94Ru∗ fusion-evaporation reaction at the Grand Accelerateur National d’Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from γ-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm2 metallic 58Ni target. In total eight excited-state lifetimes in the angular momentum range I = (13 − 20)ħ have been measured, five of which were determined for the first time. The deduced corresponding B(M1) and B(E2)reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.
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19.
  • Ertoprak, Aysegul, et al. (författare)
  • M1 and E2 transition rates from core-excited states in semi-magic Ru-94
  • 2018
  • Ingår i: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 54:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of high-spin states have been measured in the semi-magic (N = 50) nucleus Ru-94. Excited states in Ru-94 were populated in the Ni-58(Ca-40, 4p)Ru-94* fusion-evaporation reaction at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from gamma-rays emitted while the residual nuclei were slowing down in a thick 6 mg/cm(2) metallic Ni-58 target. In total eight excited-state lifetimes in the angular momentum range I = (13-20)h have been measured, five of which were determined for the first time. The corresponding B(M1) and B(E2) reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.
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20.
  • Gillespie, S. A., et al. (författare)
  • Identification of a 6.6 μ s isomeric state in Ir 175
  • 2019
  • Ingår i: Physical Review C. - 2469-9985. ; 99:6
  • Tidskriftsartikel (refereegranskat)abstract
    • An experiment has been performed to study excited states in the neutron-deficient nucleus Ir175 via the use of the JUROGAM II high-purity germanium detector array and the RITU gas-filled separator at JYFL, Jyväskylä. By using isomer tagging, an isomeric state with a half-life of 6.58(15) μs has been observed in Ir175 for the first time. It has been established that the isomer decays via a 45.2 (E1)-26.1 (M1) keV cascade to new states below the previously reported ground state in Ir175 with Iπ=(5/2-). We now reassign this (5/2-) state to the isomeric state discovered in this study.
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21.
  • Gillespie, S. A., et al. (författare)
  • Identification of sub- μ s isomeric states in the odd-odd nucleus Au 178
  • 2021
  • Ingår i: Physical Review C. - 2469-9985. ; 103:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The neutron-deficient gold (Z=79) isotopes in the vicinity of the neutron midshell N=104 provide prolific examples of shape coexistence and isomerism at low excitation energy. They can be probed via a number of different experimental techniques. In this study, two new isomeric states with half-lives of 294(7) and 373(9) ns have been observed in the neutron-deficient odd-odd nuclide Au178 (N=99) in an experiment at the RITU gas-filled separator at JYFL, Jyväskylä. This result was achieved due to the use of a segmented planar germanium detector with a high efficiency at low energies. By applying the recoil-decay tagging technique, they were assigned to decay to two different long-lived α-decaying states in Au178.
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22.
  • Lewis, M. C., et al. (författare)
  • Decay of a 19(-) isomeric state in Lu-156
  • 2018
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 98:2
  • Tidskriftsartikel (refereegranskat)abstract
    • A multiparticle spin-trap isomeric state having a half-life of 179(4) ns and lying 2601 keV above the yrast 10(+) state in Lu-156 has been discovered. The Lu-156 nuclei were produced by bombarding isotopically enriched Cd-106 targets with beams of Ni-58 ions, separated in flight using the gas-filled separator RITU and their decays were measured using the GREAT spectrometer. Analysis of the main decay path that populates yrast states observed previously suggests a spin-parity assignment of 19(-) for the isomeric state, which is consistent with isomeric states identified in the N = 85 isotones. Comparison with other decay paths in Lu-156 indicates that the [pi h(11/)(2)(-1) circle times nu h(9/2)]10(+) state at the bottom of the yrast sequence is likely to be the a-decaying isomeric state, with the [pi h(11/)(2)(-1) circle times nu f(7/2)]9(+) state lying 62 keV above it. The relative ordering of the lowest-lying 9(+) and 10(+) states is inverted in Lu-156 compared with its odd-odd isotones.
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23.
  • Parr, E., et al. (författare)
  • Identification of the J(pi)=1(-) state in Ra-218 populated via alpha decay of Th-222
  • 2016
  • Ingår i: PHYSICAL REVIEW C. - 2469-9985. ; 94:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The alpha decay of Th-222 populating the low-lying J(pi) = 3(-) state, and also a proposed 1(-) state, in Ra-218 has been observed. The observations suggest an excitation energy of 853 keV for the 1(-) state, which is 60 keV above the 3(-) state. The hindrance factors of these alpha decays give a possible boundary to the region of ground-state octupole deformation in the light-actinide nuclei. The relative positions of the J(pi) = 1(-) and 3(-) states suggest they are produced by an octupole-vibrational mechanism, as opposed to alpha clustering or rotations of a reflection-asymmetric octupole-deformed shape.
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24.
  • Wadsworth, R., et al. (författare)
  • THE NORTHWEST FRONTIER : SPECTROSCOPY OF N similar to Z NUCLEI BELOW MASS 100
  • 2009
  • Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 40:3, s. 611-620
  • Tidskriftsartikel (refereegranskat)abstract
    • The spectroscopy and structure of excited states of N similar to Z nuclei in the mass 70-100 region has been investigated using two techniques. In the A similar to 70-80 region fusion evaporation reactions coupled with the recoil-beta-tagging method have been employed at Jyvaskyla to study low-lying states in odd-odd N = Z nuclei. Results from these and other data for known odd-odd nuclei above mass 60 will be discussed. In the heavier mass 90 region a fragmentation experiment has been performed using the RIS-ING/FRS setup at GSI. This experiment was primarily aimed at searching for spin gap isomers in nuclei around A similar to 96. The objectives of the latter experiment will be discussed.
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25.
  • Briselet, R., et al. (författare)
  • Production cross section and decay study of Es 243 and Md 249
  • 2019
  • Ingår i: Physical Review C. - 2469-9985. ; 99:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In the study of the odd-Z, even-N nuclei Es243 and Md249, performed at the University of Jyväskylä, the fusion-evaporation reactions Au197(Ca48,2n)Es243 and Tl203(Ca48,2n)Md249 have been used for the first time. Fusion-evaporation residues were selected and detected using a gas-filled separator coupled with its focal-plane spectrometer. For Es243, the recoil decay correlation analysis yielded a half-life of 24±3s and a maximum production cross section of 37±10nb. In the same way, a half-life of 26±1s, an α-branching ratio of 75±5%, and a maximum production cross section of 300±80nb were determined for Md249. The decay properties of Es245, the daughter of Md249, were also measured: an α-branching ratio of 54±7% and a half-life of 65±6s. Experimental cross sections were compared to the results of calculations performed using the kewpie2 statistical fusion-evaporation code.
  •  
26.
  • Doncel, Maria, et al. (författare)
  • Lifetime measurement of the first excited 2(+) state in Te-112
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 91:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The lifetime of the 2(+) --> 0(g.s.)(+) transition in the neutron-deficicient nucleus Te-112 has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is B(E2 :0(g.s.)(+) --> 2(+)) = 0.46 +/- 0.04 e(2)b(2), indicating that there is no unexpected enhancement of the B(E2 :0(g.s.)(+) --> 2(+)) values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations.
  •  
27.
  • Doncel, Maria, et al. (författare)
  • Spin-dependent evolution of collectivity in Te 112
  • 2017
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 96:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus Te112 has been studied by measuring the reduced transition probability of excited states in the yrast band. In particular, the lifetimes of the 4+ and 6+ excited states have been determined by using the recoil distance Doppler-shift method. The results are discussed using both large-scale shell-model and total Routhian surface calculations.
  •  
28.
  • Ertoprak, Aysegul, et al. (författare)
  • Lifetime measurements of core-excited states in semi-magic 95Rh
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Lifetimes of negative-parity states have been determined in the semi-magic (N=50) nucleus 95Rh. The fusion-evaporation reaction 58Ni(40Ca, 3p) was used to populate high-spin states in 95Rh at the Grand Accelerateur National d'Ions Lourds (GANIL) accelerator facility. The results were obtained using the Doppler Shift Attenuation Method (DSAM) based on the Doppler broadened line shapes produced during the slowing down process of the residual nuclei in a thick 6~ mg/cm2 metallic target.  B(M1) and B(E2) reduced transition strengths are compared with predictions from large-scale shell-model calculations.
  •  
29.
  • Hadinia, Baharak, et al. (författare)
  • Identification of gamma rays from Au-172 and alpha decays of Au-172, Ir-168, and Re-164
  • 2009
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 80:6, s. 064310-
  • Tidskriftsartikel (refereegranskat)abstract
    • The very neutron deficient odd-odd nucleus Au-172 was studied in reactions of 342 and 348 MeV Kr-78 beams with an isotopically enriched Ru-96 target. The alpha decays previously reported for Au-172 were confirmed and the decay chain extended down to Tm-152 through the discovery of a new alpha-decaying state in Re-164 [E-alpha=5623(10) keV; t(1/2)=864(-110)(+150) ms; b(alpha)=3(1)%]. Fine structure in these alpha decays of Au-172 and Ir-168 were identified. A new alpha-decaying state was also observed and assigned as the ground state in Au-172 [E-alpha=6762(10) keV; t(1/2)=22(-5)(+6) ms]. This decay chain was also correlated down to Tm-152 through previously reported alpha decays. Prompt gamma rays from excited states in Au-172 have been identified using the recoil-decay tagging technique. The partial level scheme constructed for Au-172 indicates that it has an irregular structure. Possible configurations of the alpha-decaying states in Au-172 are discussed in terms of the systematics of nuclei in this region and total Routhian surface calculations.
  •  
30.
  • Hodge, D., et al. (författare)
  • Identification of a dipole band above the Iπ=31/2- isomeric state in Pb 189
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X. ; 92:5
  • Tidskriftsartikel (refereegranskat)abstract
    • A dipole band of six transitions built upon a firmly established Iπ=31/2- isomeric state has been identified in Pb189 using recoil-isomer tagging. This is the lightest odd-mass Pb nucleus in which a dipole band is known. The dipole nature of the new transitions has been confirmed through angular-intensity arguments. The evolution of the excitation energy and the aligned-angular momentum of the states in the new dipole band are compared with those of dipole bands in heavier, odd-mass lead isotopes. This comparison suggests that the new band in Pb189 is based upon a π[s1/2-2h9/2i13/2]11- - ν[i13/2+-1]13/2+ configuration. However, the increased aligned-angular momentum in Pb189 may suggest evidence for a reduced repulsive proton/neutron-hole interaction compared to dipole bands in the heavier mass isotopes.
  •  
31.
  • Hornillos, M. B. G., et al. (författare)
  • gamma-ray spectroscopy approaching the limits of existence of atomic nuclei : A study of the excited states of Pt-168 and Pt-169
  • 2009
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 79:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the N=90 and N=91 Pt nuclei have been investigated using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator. These nuclei were populated via the reactions Mo-92(Kr-78,2n) and Mo-94(Kr-78,3n) at 335 and 348 MeV, respectively. The recoil-decay tagging technique has been used to correlate prompt gamma radiation with the characteristic alpha decays of Pt-168 and Pt-169. A gamma-gamma analysis has allowed a level scheme for Pt-168 to be reported for the first time and the level scheme for Pt-169 to be extended. The excitation energies of the proposed positive-parity yrast states of Pt-168 are compared with calculations based on the interacting boson model and found to be in excellent agreement. These data show a continuation of the trend toward vibrational nuclei as the N=82 shell gap is approached. In addition, new excited states constituting two decay paths have been discovered in Pt-169. .  
  •  
32.
  • Ketelhut, S., et al. (författare)
  • gamma-Ray Spectroscopy at the Limits : First Observation of Rotational Bands in Lr-255
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:21, s. 212501-
  • Tidskriftsartikel (refereegranskat)abstract
    • The rotational band structure of Lr-255 has been investigated using advanced in-beam gamma-ray spectroscopic techniques. To date, Lr-255 is the heaviest nucleus to be studied in this manner. One rotational band has been unambiguously observed and strong evidence for a second rotational structure was found. The structures are tentatively assigned to be based on the 1/2(-)[521] and 7/2(-)[514] Nilsson states, consistent with assignments from recently obtained alpha decay data. The experimental rotational band dynamic moment of inertia is used to test self-consistent mean-field calculations using the Skyrme SLy4 interaction and a density-dependent pairing force.
  •  
33.
  • Leguillon, R., et al. (författare)
  • High-spin spectroscopy of Nd-140
  • 2013
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The population of the high-spin states in Nd-140 was investigated using the reaction Zr-96(Ca-48,4n). The results from two experiments, one with the EUROBALL array and one with the JUROGAM II + RITU + GREAT setup employing the recoil decay tagging technique, have been combined to develop a very detailed level scheme for Nd-140. Twelve bands of quadrupole transitions and eleven bands of dipole transitions were identified and their connections to low-lying states were established. Calculations using the cranked Nilsson-Strutinsky and the tilted axis cranking models were used to interpret the observed structures. The overall good agreement between the experimental results and the calculations assuming a triaxial shape of the nucleus strongly support the existence of a stable triaxial shape at high spins in this mass region.
  •  
34.
  • Lv, B. F., et al. (författare)
  • Evolution from γ -soft to stable triaxiality in Nd 136 as a prerequisite of chirality
  • 2018
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 98:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The level structure of Nd136 has been investigated using the Mo100(Ar40,4n) reaction and the JUROGAM II+RITU+GREAT setup. The level scheme has been extended significantly. Many new bands have been identified both at low and high spin, among which are five nearly degenerate bands interpreted as chiral partners. Excitation energies, spins, and parities of the previously known bands are revised and firmly established, and some previously known bands have been revised. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. The band structure of Nd136 is now clarified and the various types of single-particle and collective excitations are well understood.
  •  
35.
  • Pereira-López, X., et al. (författare)
  • In-beam γ -ray spectroscopy of 94 Ag
  • 2023
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 59:3
  • Tidskriftsartikel (refereegranskat)abstract
    • A recoil-beta-tagging experiment has been performed to study the excited T= 0 and T= 1 states in the odd–odd N= Z nucleus 94Ag, populated via the 40Ca(58Ni,1p3n)94Ag reaction. The experiment was conducted using the MARA recoil separator and JUROGAM3 array at the Accelerator Laboratory of the University of Jyväskylä. Through correlating fast, high-energy beta decays at the MARA focal plane with prompt γ rays emitted at the reaction target, a number of transitions between excited states in 94Ag have been identified. The timing characteristics of these transitions confirm that they fall within decay sequences that feed the short-lived T= 1 ground state of 94Ag. The transitions are proposed to proceed within and between the sets of states with T= 0 and T= 1. Possible correspondence between some of these transitions from analog states in 94Pd has been discussed, and shell-model calculations including multipole and monopole electromagnetic effects have been presented, in order to enable predictions of the decay patterns between the T= 0 and T= 1 states and to allow a theoretical set of Coulomb energy differences to be calculated for the A= 94 T= 1 analog states.
  •  
36.
  • Petri, M., et al. (författare)
  • Nuclear levels in proton-unbound I-109 : Relative single-particle energies beyond the proton drip line
  • 2007
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 76:5
  • Tidskriftsartikel (refereegranskat)abstract
    • A level scheme has been constructed for the proton-unbound, T-z=3/2 nuclide I-109(53)56 following a recoil-decay-tagging experiment using the Ni-58(Fe-54, p2n gamma) reaction at a beam energy of 195 MeV. The experiment was performed using the highly efficient JUROGAM gamma-ray spectrometer in conjunction with the RITU gas-filled recoil separator and the GREAT focal-plane spectrometer. Cranking calculations are used to interpret band structures built on pi g(7/2) and pi h(11/2) states in a weakly deformed, triaxial nucleus.
  •  
37.
  • Singh, B. S. Nara, et al. (författare)
  • Coulomb shifts and shape changes in the mass 70 region
  • 2007
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 75:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The technique of recoil beta tagging has been developed which allows prompt gamma decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived beta decay. This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in Y-78 to be observed for the first time, as well as an extension in the knowledge of T=1 states in Rb-74. From this new information it has been possible to compare Coulomb energy differences (CED) between T=1 states in Br-70/Se-70, Rb-74/Kr-74, and Y-78/Sr-78. The A=70 CED exhibit an anomalous behavior which is inconsistent with all other known CED. This behavior may be accounted for qualitatively in terms of small variations in the Coulomb energy arising from shape changes.
  •  
38.
  • Taylor, M. J., et al. (författare)
  • Competing single-particle and collective states in the low-energy structure of I-113
  • 2013
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 88:5, s. 054307-
  • Tidskriftsartikel (refereegranskat)abstract
    • To understand the low-energy structure of the neutron deficient iodine isotopes, lifetimes for the low-lying 9/2(+) and 11/2(+) positive-parity states in I-113 have been measured as tau = 28(4) ps and tau = 3.7(7) ps, respectively. The lifetime for the 11/2(-) state, which feeds the 9/2(+) and 11/2(+) states, was remeasured with improved accuracy as tau = 216(7) ps. The reduced transition probability, B(E2) = 32(5) W.u., for the 9/2(+) -> 5/2(+) transition agrees with that calculated within the shell model using a Hamiltonian based on the charge-dependent Bonn nucleon-nucleon interaction. In contrast, the much larger transition probability, B(E2) = 209(39) W.u., measured for the 11/2(+) -> 7/2(+) transition has been interpreted, with the aid of configuration-constrained total Routhian surface calculations, as resulting from a slightly gamma-soft rotor with an associated quadrupole deformation of beta(2) approximate to 0.18. Remarkably similar reduced E1 transition probabilities of 5.5(5) x 10(-4) and 4.9(5) x 10(-4) W.u. were deduced for the 11/2(-) -> 9/2(+) and 11/2(-) -> 11/2(+) transitions, respectively, which feed apparently dissimilar but competing structures.
  •  
39.
  • Taylor, M. J., et al. (författare)
  • Oblately deformed isomeric proton-emitting state in Lu-151
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 91:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Gamma rays from excited states feeding a proton-emitting isomeric-state in Lu-151 have been observed for the first time. Comparison with state-of-the-art nonadiabatic quasiparticle calculations indicates an oblately deformed, 3/2(+) proton-emitting state with a quadrupole deformation of beta(2) = -0.11. The calculations suggest an increase in quadrupole deformation, to beta(2) = -0.18, with increasing spin which is understood in terms of the mixing of Nilsson states at the Fermi surface. It is also shown that the proton decay half-life is consistent with that from a 3/2(+) state with a quadrupole deformation of beta(2) = -0.12.
  •  
40.
  • Carroll, R. J., et al. (författare)
  • Blurring the Boundaries : Decays of Multiparticle Isomers at the Proton Drip Line
  • 2014
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:9, s. 092501-
  • Tidskriftsartikel (refereegranskat)abstract
    • A multiparticle spin-trap isomer has been discovered in the proton-unbound nucleus 158 73 Ta 85. The isomer mainly decays by (h) over bar -ray emission with a half-life of 6.1d(1) mu s. Analysis of the gamma-ray data shows that the isomer lies 2668 keV above the known 9(+) state and has a spin 10h higher and negative parity. This 19(-) isomer also has an 8644(11) keV, 1.4(2)% alpha-decay branch that populates the 9(+) state in Lu-154. No proton-decay branch from the isomer was identified, despite the isomer being unbound to proton emission by 3261(14) keV. This remarkable stability against proton emission is compared with theoretical predictions, and the implications for the extent of observable nuclides are considered.
  •  
41.
  • Carroll, R. J., et al. (författare)
  • Competing decay modes of a high-spin isomer in the proton-unbound nucleus 158Ta
  • 2015
  • Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 46:3, s. 695-698
  • Tidskriftsartikel (refereegranskat)abstract
    • An isomeric state at high spin and excitation energy was recently observed in the proton-unbound nucleus 158Ta. This state was observed to decay by both α and γ decay modes. The large spin change required to decay via γ-ray emission incurs a lifetime long enough for α decay to compete. The α decay has an energy of 8644(11) keV, which is among the highest observed in the region, a partial half-life of 440(70) μs and changes the spin by 11h. In this paper, additional evidence supporting the assignment of this α decay to the high-spin isomer in 158Ta will be presented.
  •  
42.
  • Doncel, Maria, et al. (författare)
  • Lifetime measurements of excited states in W-162 and W-164 and the evolution of collectivity in rare-earth nuclei
  • 2017
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 95:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Lifetimes of the first excited 2(+) states in the extremely neutron- deficient W-162 and W-164 nuclei have been measured using the recoil distance Doppler shift technique. Experimental B(E2) data for the isotopic chains of hafnium, tungsten, and osmium, from the midshell region near the beta-stability line towards the N = 82 closed shell and the most neutron-deficient nuclides, are compared with predictions of nuclear deformations and 2(1)(+) -> 0(g.s)(.+) reduced transition strengths from different classes of state-of-the-art theoretical model calculations. The results reveal striking differences and deficiencies in the predictive power of current nuclear structure models.
  •  
43.
  • Ghazi Moradi, Farnaz, et al. (författare)
  • High-spin study of 162Ta
  • 2011
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 84:6, s. 064312-
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
  •  
44.
  • Hadinia, Baharak, et al. (författare)
  • First identification of gamma-rays in Te-106 using recoil decay tagging technique
  • 2006
  • Ingår i: Frontiers in Nuclear Structure Astrophysics, and Reactions: FINUSTAR. - MELVILLE, NY : AMER INST PHYSICS. - 0735403236 - 9780735403239 ; , s. 457-459
  • Konferensbidrag (refereegranskat)abstract
    • Gamma-ray transitions from excited states in Te-106 have been identified using the recoil decay tagging technique. The experiment which was the reaction Fe-54(Fe-54,2n)Te-106* was performed at the JYFL accelerator facility at the University of Jyvaskyla, Finland. The production cross section was estimated at 25 nb, a new limit for in-beam gamma-ray spectroscopy. A tentative level structure for the ground state band of Te-106 is proposed.
  •  
45.
  • Herzan, A., et al. (författare)
  • Detailed spectroscopy of Bi-195
  • 2017
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 96:1
  • Tidskriftsartikel (refereegranskat)abstract
    • An experiment focused on the study of shape coexistence and new high-spin structures in Bi-195 has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the 13/2(+) isomeric state was extended up to I-pi = (49/2(+)) and an energy of 5706 keV. The I-pi = 31/2(+) member of the pi i(13/2) band was also found to feed a new long-lived isomeric state with an excitation energy of 2616 keV and a spin and parity of I-pi = 29/2(+). The half-life of the 29/2+ isomeric state was determined to be 1.49(1) mu s. It decays via the emission of 457-keV E2 and 236-keV E1 transitions, respectively. A low-energy 46-keV E2 transition has been identified to depopulate the (29/(2-)) isomeric state, with a measured half-life of T-1/2 = 614(5) ns. This transition allows the excitation energy of the isomeric state to be determined as 2381 keV. The feeding patterns of both 29/2(+) and (29/2(-)) isomeric states have also been described. This is the first time collective structures have also been observed up to high spins and excitation energies in the neutron-deficient Bi-195 nucleus. Evidence for the manifestation of shape coexistence in Bi-195 is also discussed.
  •  
46.
  • Jakobsson, Ulrika, et al. (författare)
  • Spectroscopy of Low-lying States in Neutron-deficient Astatine and Francium Nuclei
  • 2015
  • Ingår i: NUCLEAR STRUCTURE AND DYNAMICS '15. - : American Institute of Physics (AIP). - 9780735413283
  • Konferensbidrag (refereegranskat)abstract
    • Low-lying states in neutron-deficient astatine and francium nuclei have been studied by means of in-beam and delayed spectroscopy. The 13/2(+) state has been observed in francium nuclei with a similar down-sloping trend as in neighbouring astatine and bismuth isotopes, as a function of decreasing neutron number. A systematic trend can also now be seen for the 1/2(+) state both in astatine and francium nuclei, where the level energy decreases steeply as a function of neutron number when moving further away from the neutron shell closure. This trend is very similar between astatine nuclei and their francium isotones. Moreover, shape coexistence has been observed between the 13/2(+) state and the spherical 9/2(-) ground state in Fr-203 and Fr-205.
  •  
47.
  • Joss, D. T., et al. (författare)
  • Spectroscopy at the two-proton drip line : Excited states in 158W
  • 2017
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 772, s. 703-707
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states have been identified in the heaviest known even-Z N=84 isotone 158W, which lies in a region of one-proton emitters and the two-proton drip line. The observation of γ-ray transitions feeding the ground state establishes the excitation energy of the yrast 6+ state confirming the spin-gap nature of the α-decaying 8+ isomer. The 8+ isomer is also expected to be unbound to two-proton emission but no evidence for this decay mode was observed. An upper limit for the two-proton decay branch has been deduced as b2p≤ 0.17% at the 90% confidence level. The possibility of observing two-proton emission from multiparticle isomers in nearby nuclides is considered.
  •  
48.
  • Li, Hongjie, et al. (författare)
  • First identification of rotational band structures in Re-166(75)91
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 92:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the odd-odd, highly neutron-deficient nucleus Re-166 have been investigated via the Mo-92(Kr-78, 3p1n)Re-166 reaction. Prompt gamma rays were detected by the JUROGAM II. gamma-ray spectrometer, and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and implanted into the Gamma Recoil Electron Alpha Tagging spectrometer located at the RITU focal plane. The tagging and coincidence techniques were applied to identify the gamma-ray transitions in Re-166, revealing two collective, strongly coupled rotational structures, for the first time. The more strongly populated band structure is assigned to the pi h(11/2)[514]9/2(-) circle times vi(13/2)[660]1/2(+) Nilsson configuration, while the weaker structure is assigned to be built on a two-quasiparticle state of mixed pi h(11/2)[514]9/2(-) circle times v[h(9/2)f(7/2)]3/2(-) character. The configuration assignments are based on the electromagnetic characteristics and rotational properties, in comparison with predictions from total Routhian surface and particle-rotor model calculations.
  •  
49.
  • Li, Hongjie, et al. (författare)
  • Recoil-decay tagging spectroscopy of W-162(74)88
  • 2015
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 92:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in the highly neutron-deficient nucleus W-162 have been investigated via the Mo-92(Kr-78, 2 alpha) W-162 reaction. Prompt gamma rays were detected by the JUROGAM II high-purity germanium detector array and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and identified with the gamma recoil electron alpha tagging (GREAT) spectrometer at the focal plane of RITU. gamma rays from W-162 were identified uniquely using mother-daughter and mother-daughter-granddaughter alpha-decay correlations. The observation of a rotational-like ground-state band is interpreted within the framework of total Routhian surface (TRS) calculations, which suggest an axially symmetric ground-state shape with a gamma-soft minimum at beta(2) approximate to 0.15. Quasiparticle alignment effects are discussed based on cranked shell model calculations. New measurements of the W-162 ground-state alpha-decay energy and half-life were also performed. The observed alpha-decay energy agrees with previous measurements. The half-life of W-162 was determined to be t(1/2) = 990(30) ms. This value deviates significantly from the currently adopted value of t(1/2) = 1360(70) ms. In addition, the alpha-decay energy and half-life of Os-166 were measured and found to agree with the adopted values.
  •  
50.
  • Lv, B. F., et al. (författare)
  • Chirality of Nd-135 reexamined : Evidence for multiple chiral doublet bands
  • 2019
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 100:2
  • Tidskriftsartikel (refereegranskat)abstract
    • One new pair of positive-parity chiral doublet bands have been identified in the odd-A nucleus Nd-135 which together with the previously reported negative-parity chiral doublet bands constitute a third case of multiple chiral doublet (M chi D) bands in the A approximate to 130 mass region. The properties of the M chi D bands are well reproduced by constrained covariant density functional theory and particle rotor model calculations. The newly observed M chi D bands in Nd-135 represents an important milestone in supporting the existence of M chi D in nuclei.
  •  
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