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Employing the recoil ion transport unit (RITU) and a fusion-evaporation reaction, the α decay of 211Pa has been identified via the implantation-decay correlation technique through observation of chains up to four consecutive decays. An α-particle energy and half-life of 8320(40) keV and 3.8+4.6−1.4 ms, respectively, were measured, corresponding to favored α decay. In addition, more precise α-decay properties of 212Pa and 213Pa were obtained due to accumulated statistics. The present data were compared to those predicted by selected atomic mass models and it was used to estimate the possibility of observing proton emission from these isotopes. peerReviewed

The extremely neutron-deficient isotopes 177,179Au were studied by means of in-beam ?-ray spectroscopy. Specific tagging techniques, ?-decay tagging in 177Au and isomer tagging in 179Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2d3/2 and 3s1/2 proton-hole configurations, from the 1i13/2 proton-intruder configuration was observed in 177Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state. © 2020, 262010 2/0129/17 Science and Technology Facilities Council, STFC European Research Council, ERC: 203481 Academy of Finland: 131665 Agentúra na Podporu V?skumu a V?voja, APVV: APVV-15-0225, The authors express their gratitude to the staff of the Accelerator Laboratory at the University of Jyväskylä for their excellent technical support. This work has been supported by the EU-FP7-IA project ENSAR (No. 262010 ), the Academy of Finland (CoE in Nuclear and Accelerator Based Physics, grant to T.G., Contract No. 131665 ), the European Research Council through the project SHESTRUCT (Grant Agreement No. 203481 ), the UK Science and Technology Facilities Council , the Slovak Research and Development Agency under Contract No. APVV-15-0225 , and the Slovak Grant Agency VEGA (Contract No. 2/0129/17 ).

The mean lifetimes of the lowest energy 2(+), 8(+) and 9(-) states in Os-166 have been measured using the recoil distance Doppler-shift method in conjunction with a selective recoil-decay tagging t ...

A new automated method has been developed with the aim to correct measured spectra for sudden gain and offset drifts due to temporal instrumentation instabilities. It is based on discrete cross-correlation that alleviates the need for Gaussian-shaped peaks and is capable of correcting spectra that change their shape in time. Potential of this method has been tested on decay and in-beam γ -ray spectroscopy data measured with an array of three n-type coaxial High-Purity Germanium detectors albeit its use is not limited only for γ -ray spectroscopy.

© 2019 American Physical Society. An analysis technique has been developed in order to mitigate energy summing due to sequential short-lived α decays from nuclei implanted into a silicon detector. Using this technique, α-decay spectroscopy of the N=130 isotones Ra218 (Z=88) and Th220 (Z=90) has been performed. The energies of the α particles emitted in the Ra218→Rn214 and Th220→Ra216 ground-state-to-ground-state decays have been measured to be 8381(4) keV and 8818(13) keV, respectively. The half-lives of the ground states of Ra218 and Th220 have been measured to be 25.99(10) μs and 10.4(4) μs, respectively. The half-lives of the ground states of the α-decay daughters, Rn214 and Ra216, have been measured to be 259(3) ns and 161(11) ns, respectively. Fine structure in the α decay of Ra218 has been observed for the first time, populating the 695-keV 21+ state in Rn214. The fine-structure α decay has an α-particle energy of 7715(40) keV and branching ratio bα=0.123(11)%.

An analysis technique has been developed in order to mitigate energy summing due to sequential short-lived α decays from nuclei implanted into a silicon detector. Using this technique, α-decay spectroscopy of the N=130 isotones Ra218 (Z=88) and Th220 (Z=90) has been performed. The energies of the α particles emitted in the Ra218→Rn214 and Th220→Ra216 ground-state-to-ground-state decays have been measured to be 8381(4) keV and 8818(13) keV, respectively. The half-lives of the ground states of Ra218 and Th220 have been measured to be 25.99(10) μs and 10.4(4) μs, respectively. The half-lives of the ground states of the α-decay daughters, Rn214 and Ra216, have been measured to be 259(3) ns and 161(11) ns, respectively. Fine structure in the α decay of Ra218 has been observed for the first time, populating the 695-keV 21+ state in Rn214. The fine-structure α decay has an α-particle energy of 7715(40) keV and branching ratio bα=0.123(11)%.

Lifetime measurements of excited states in 178 Hg have been performed using the 103 Rh ( 78 Kr , p 2 n ) reaction at a beam energy of 354 MeV. The recoil-decay tagging (RDT) technique was applied to select the 178 Hg nuclei and associate the prompt γ rays with the correlated characteristic ground-state α decay. Lifetimes of the four lowest yrast states of 178 Hg have been determined using the recoil distance Doppler-shift (RDDS) method. The experimental data are compared to theoretical predictions with focus on shape coexistence. The results confirm the shift of the deformed prolate structures to higher lying states but also indicate their increasing deformation with decreasing neutron number. peerReviewed

Grahn, Tuomas/0000-0002-6255-2279; Herzan, Andrej/0000-0002-6736-7638; Cullen, Dave/0000-0002-0041-1606; Barber, Liam/0000-0002-7409-9352; Keatings, James Michael/0000-0003-4271-8021; SAYGI, BAHADIR/0000-0001-5406-506X; Greenlees, Paul/0000-0002-5986-5274; Spagnoletti, Pietro/0000-0002-7674-989X; Parr, Edward/0000-0001-6204-4461; Bondili, S Nara Singh/0000-0002-4096-2429, WOS: 000494939000022, This letter reports lifetime measurements of excited states in the odd-N nucleus W-163 using the recoil-distance Doppler shift method to probe the core polarising effect of the i(13/2) neutron orbital on the underlying soft triaxial even-even core. the ratio B(E2:21/2(+) -> 17/2(+))/B(E2:17/2(+) -> 13/2(+)) is consistent with the predictions of the collective rotational model. the deduced B(E2) values provide insights into the validity of collective model predictions for heavy transitional nuclei and a geometric origin for the anomalous B(E2) ratios observed in nearby even-even nuclei is proposed. (C) 2019 the Authors. Published by Elsevier B.V., UK Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC) [ST/P004598/1, ST/L005670/1, ST/L005794/1]; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [117F508]; EU HORIZON2020 programme "Infrastructures" [654002]; Academy of Finland under the Finnish Centre of Excellence Programme (Nuclear and Accelerator Based Physics Programme at JYFL); Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC) [1643549] Funding Source: researchfish, This work has been supported by the UK Science and Technology Facilities Council under grants ST/P004598/1, ST/L005670/1 and ST/L005794/1; the Scientific and Technological Research Council of Turkey (TUBITAK Project No: 117F508); the EU HORIZON2020 programme "Infrastructures", project number: 654002 (ENSAR2) and by the Academy of Finland under the Finnish Centre of Excellence Programme (Nuclear and Accelerator Based Physics Programme at JYFL). the UK/France (STFC/IN2P3) Loan Pool and GAMMAPOOL network are acknowledged for the HPGe escapesuppressed detectors of the JUROGAM II array.

Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of ²⁰³At (N = 118) significantly. We have observed an isomeric [τ=14.1(3)μs] state with a spin and parity of 29/2+. The isomeric state is suggested to originate from the π(h9/2)⊗∣∣²⁰²Po;11⁻⟩ coupling, and it is depopulated through 286 keV E2 and 366 keV E3 transitions. In addition, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism.

The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus $^{112}\mathrm{Te}$ 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.

Excited states in the proton-unbound nuclide $^{177}$Au were populated in the $^92}$Mo($^{88}$Sr, p2n) reaction and identified using the Jurogam-II and GREAT spectrometers in conjunction with the RITU gas-filled separator at the University of Jyvaskyla Accelerator Laboratory. A strongly coupled band and its decay path to the 11/2−α-decaying isomer have been identified using recoil-decay tagging. Comparisons with cranked Hartree-Fock-Bogoliubov (HFB) calculations based on Skyrme energy functionals suggest that the band has a prolate deformation and is based upon coupling the odd 1h11/2 proton hole to the excited 02+ configuration in the $^{178}$Hg core. Although these configurations might be expected to follow the parabolic trend of core Hg(02+) states as a function of neutron number, the electromagnetic decay paths from the strongly coupled band in $^{177}$Au are markedly different from those observed in the heavier isotopes above the midshell. This indicates that a significant change in the structure of the underlying A+1Hg core occurs below the neutron midshell.

The neutron-deficient ${}^{\mathrm{196,198}}$Pb isotopes have been studied in Coulomb-excitation experiments employing the Miniball γ-ray spectrometer and radioactive ion beams from the REX-ISOLDE post-accelerator at CERN. The reduced transition probabilities of the first excited 2+ states in 196Pb and 198Pb nuclei have been measured for the first time. Values of $B(E2)={18.2}_{-4.1}^{+4.8}$ W.u. and $B(E2)={13.1}_{-3.5}^{+4.9}$ W.u., were obtained, respectively. The experiment sheds light on the development of collectivity when moving from the regime governed by the generalised seniority scheme to a region, where intruding structures, associated with different deformed shapes, start to come down in energy and approach the spherical ground state. journal_title: Journal of Physics G: Nuclear and Particle Physics article_type: paper article_title: Collectivity in ${}^{\mathrm{196,198}}$Pb isotopes probed in Coulomb-excitation experiments at REX-ISOLDE copyright_information: © 2017 IOP Publishing Ltd date_received: 2016-10-31 date_accepted: 2017-03-17 date_epub: 2017-05-03 ispartof: Journal of Physics G, Nuclear and Particle Physics vol:44 issue:6 status: published

A newly observed isomeric intruder -+ state [T-=3.5(6)ms] is identified in At203 using a gas-filled recoil separator and fusion-evaporation reactions. The isomer is depopulated through a cascade of E3 and mixed M1/E2 transitions to the 9/2- ground state, and it is suggested to originate from the π(s-)-1 configuration. In addition, the structures above the -+ state in At203 and At197 are studied using in-beam γ-ray spectroscopy, recoil-decay tagging, and recoil-isomer decay tagging methods. The -+ state is fed from 3/2+ and 5/2+ states, and the origin of these states are discussed.

Excited states in the proton-unbound nucleus 151Lu have been established using γ-ray coincidence techniques. The lifetime of the first excited state above the proton-emitting ground state has been measured using the recoil-distance Doppler-shift method combined with recoil-decay tagging. The experimental level scheme and extracted lifetime have been compared with state-of-the-art theoretical calculations based upon a non-adiabatic deformed Woods–Saxon potential. This comparison suggests that the proton-emitting ground state in 151Lu is mildly oblate with a deformation β = − 0.11 − 0.05 + 0.02 and represents the best evidence to date for proton emission from an oblate nucleus.

The $\ensuremath{\alpha}$ decay of $^{222}\mathrm{Th}$ populating the low-lying ${J}^{\ensuremath{\pi}}={3}^{\ensuremath{-}}$ state, and also a proposed ${1}^{\ensuremath{-}}$ state, in $^{218}\mathrm{Ra}$ has been observed. The observations suggest an excitation energy of 853 keV for the ${1}^{\ensuremath{-}}$ state, which is 60 keV above the ${3}^{\ensuremath{-}}$ state. The hindrance factors of these $\ensuremath{\alpha}$ decays give a possible boundary to the region of ground-state octupole deformation in the light-actinide nuclei. The relative positions of the ${J}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ and ${3}^{\ensuremath{-}}$ states suggest they are produced by an octupole-vibrational mechanism, as opposed to $\ensuremath{\alpha}$ clustering or rotations of a reflection-asymmetric octupole-deformed shape.

WOS: 000371740600004, Lifetimes of excited states in the neutron-deficient odd-odd nucleus Re-166 have been measured for the first time using the recoil distance Doppler-shift method. The measured lifetime for the (8(-)) state; tau = 480 (80) ps, enabled an assessment of the multipolarities of the gamma rays depopulating this state. Information on electromagnetic transition strengths were deduced for the gamma-ray transitions from the (9(-)), (10(-)), and (11(-)) states, and in the case of the (10(-)) and (11(-)) states limits on the B (M1) and B(E2) strengths were estimated. The results are compared with total Routhian surface predictions and semiclassical calculations. Tilted-axis cranking calculations based on a relativistic mean-field approach (TAC-RMF) have also been performed in order to test the possibility of magnetic rotation in the 166Re nucleus. While the TAC-RMF calculations predict a quadrupole-deformed nuclear shape with similar beta(2) deformation as obtained by using the TRS model, it was found that the experimental electromagnetic transition rates are in better agreement with a collective -rotational description., Swedish Research CouncilSwedish Research Council [621-2010-3694]; Academy of Finland under the Finnish Centre of Excellence ProgrammeAcademy of Finland; UK Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC); European UnionEuropean Union (EU) [262010]; China Scholarship CouncilChina Scholarship Council [201306210205]; Academy of FinlandAcademy of Finland [131665]; Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC) [ST/L005670/1, EP/E004385/1, ST/L005689/1, ST/G008671/1, ST/J000094/1, EP/C015266/1], The authors would like to thank the staff at the Accelerator Laboratory of the University of Jyvaskyla for their excellent technical support. This work was supported by the Swedish Research Council (Project No. 621-2010-3694), the Academy of Finland under the Finnish Centre of Excellence Programme 2012 - 2017, the UK Science and Technology Facilities Council, and the European Union Seventh Framework Programme Integrating Activities-Transnational Access, Project No. 262010 (ENSAR). Li is supported in part by the China Scholarship Council under Grant No. 201306210205. Additionally, we thank the GAMMAPOOL European Spectroscopy Resource for the loan of the detectors for JUROGAM II array. T.G. acknowledges the support from the Academy of Finland (Contract No. 131665).

In the present study, $B(E2; 2^{+}_{1}\rightarrow 0^{+}_{1})$ values have been measured in the 208,210Rn and 206Po nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics at CERN-ISOLDE. These nuclei have been proposed to lie in, or at the boundary of the region where the seniority scheme should persist. However, contributions from collective excitations are likely to be present when moving away from the N=126 closed shell. Such an effect is confirmed by the observed increased collectivity of the $2^{+}_{1}\rightarrow 0^{+}_{1}$ transitions. Experimental results have been interpreted with the aid of theoretical studies carried out within the BCS-based QRPA framework.

The excited states of $^{201}\mathrm{At}$ were studied and an isomeric $29/{2}^{+}$ state $[{T}_{\textonehalf{}}=3.39(9)\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{s}]$ was identified by using a fusion-evaporation reaction, a gas-filled recoil separator, and recoil gating techniques. The $29/{2}^{+}$ state is suggested to originate from the $\ensuremath{\pi}({h}_{9/2})\ensuremath{\bigotimes}|^{200}\mathrm{Po};{11}^{\ensuremath{-}}\ensuremath{\rangle}$ configuration, and it decays through the 269- and 339-keV $E2$- and $E3$-type transitions, respectively. Moreover, a cascade of magnetic dipole transitions that is suggested to originate from a shears band was observed by using recoil-gated $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}(\ensuremath{-}\ensuremath{\gamma})$ coincidence techniques.

Two experiments aiming to study the shape coexistence and competing structures in 193Bi and 195Bi isotopes have been performed at the Accelerator laboratory of the University of Jyv askyl a, Finland (JYFL). Many new states have been found, hugely extending the previously known level schemes for both isotopes. The i13=2 bands were extended up to I = 45/2+ in both the 193;195Bi isotopes. In case of 193Bi, the I = 31/2+ member of the i13=2 band was found to de-excite also to a long-lived isomeric state. This link determines the energy of the isomeric state to be 2350(1) keV and suggests a spin and parity of 29/2+. The half-life of the isomeric state was measured to be 85(3) s. A level structure on top of this isomeric state was constructed. The newly observed 49 keV E2 transition provides a link between the (29/2􀀀) isomeric state and lower-lying structures in 193Bi. A superdeformed band almost identical to that present in the neighboring isotope 191Bi has been identified. Both the 29/2+ and (29/2􀀀) isomeric states, together with the full decay-paths have also been identified in 195Bi. In both isotopes, the decay cascades from 31/2+ states to the 29/2+ isomeric states are surprisingly similar. Compared to 193Bi, measured half-lives of these isomeric states are considerably shorter in 195Bi. Experimental evidence is given proving the smaller quadrupole deformations in 195Bi when compared to 193Bi nucleus. Moreover, several new rotational collective structures have been identified in 195Bi, even though their variety is not as rich as in 193Bi. This is the first time the collective structures have been observed up to a high spins and excitation energies in 195Bi. Strong manifestation of shape coexistence is thus proved to be present also in 195Bi. Keywords

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 203Fr and 205Fr.