Low-lying states in the odd-Z isotopes Ac-221(89)132 and Pa-225(91)134 have been studied using alpha-particle and alpha gamma-coincidence spectroscopy in the Pa-225 -> Ac-221 -> Fr-217 decay chain. Ground-state spin and parity assignments of I-pi = 5/2(-) are proposed for both Ac-221 and Pa-225, with the odd proton occupying the Omega = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In Ac-221, excited states in the bands based on the Omega = 5/2 and Omega = 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.

Low-lying states in the odd-$Z$ isotopes $_{\phantom{\rule{3.33333pt}{0ex}}89}^{221}\mathrm{Ac}_{132}$ and $_{\phantom{\rule{3.33333pt}{0ex}}91}^{225}\mathrm{Pa}_{134}$ have been studied using $\ensuremath{\alpha}$-particle and $\ensuremath{\alpha}\ensuremath{\gamma}$-coincidence spectroscopy in the $^{225}\mathrm{Pa}\ensuremath{\rightarrow}^{221}\mathrm{Ac}\ensuremath{\rightarrow}^{217}\mathrm{Fr}$ decay chain. Ground-state spin and parity assignments of ${I}^{\ensuremath{\pi}}$ = ${5/2}^{\ensuremath{-}}$ are proposed for both $^{221}\mathrm{Ac}$ and $^{225}\mathrm{Pa}$, with the odd proton occupying the $\mathrm{\ensuremath{\Omega}}$ = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In $^{221}\mathrm{Ac}$, excited states in the bands based on the $\mathrm{\ensuremath{\Omega}}$ = 5/2 and $\mathrm{\ensuremath{\Omega}}$ = 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.

Excited states have been identified in the very neutron-deficient N = Z + 3 nucleus Xe-111 for the first time, using the Ni-58(Ni-58, alpha n) heavy-ion fusion-evaporation reaction. gamma-ray transitions have been unambiguously assigned to Xe-111 by correlation with the characteristic Xe-111 -> Te-107 -> Sn-103 alpha-decay chain using the method of recoil-decay tagging. Inspection of gamma gamma-coincidence data has shown that five of the transitions form a rotational-like sequence. Excitation-energy systematics suggest that the sequence could be the favored signature partner of a band built on an h(11/2) neutron. Aligned angular momenta of states in the band have been compared to analogous bands in neighboring xenon isotopes. The aligned angular momenta for the Xe-111 band are constant over the range of observed rotational frequencies, suggesting that the first pi(h(11/2))(2) alignment is either delayed or absent. It is speculated that the alignment of h(11/2) protons in the presence of neutrons in near-identical h(11/2) orbitals may be affected by neutron-proton interactions or by the onset of octupole correlations.

Fine structure in the α decay of Th90221, populating excited states in Ra88217, was studied using αγ-coincidence spectroscopy. Two α-decay branches from Th221 have been newly observed, with Eα(keV)[bα(%)]=7951(8)[0.14(3)] and 8247(3)[1.51(12)], together with three previously known branches. Also, two new states in Ra217 were identified at E = 177 and 227 keV. The ground-state configurations of the odd-A, N = 131 transitional isotones above Pb208 are interpreted from their α-decay fine structure systematics and considered in terms of predictions using spherical shell and reflection-asymmetric models.

Fine structure in the alpha decay of Th-221(90) , populating excited states in( 88)(217)Ra, was studied using alpha gamma-coincidence spectroscopy. Two alpha-decay branches from Th-221 have been newly observed, with E-alpha(keV)[b(alpha)(%)] = 7951(8)[0.14(3)] and 8247(3)[1.51(12)], together with three previously known branches. Also, two new states in Ra-217 were identified at E = 177 and 227 keV. The ground-state configurations of the odd-A, N = 131 transitional isotones above Pb-208 are interpreted from their a-decay fine structure systematics and considered in terms of predictions using spherical shell and reflection-asymmetric models.

© 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)%.

Parr, E.; Page, R.D.; Joss, D.T.; Ali, F.A.; Auranen, K.; Capponi, L.; Grahn, T.; Greenlees, P.T.; Henderson, J.; Herzan, A.; Jakobsson, U.; Julin, R.; Juutinen, S.; Konki, J.; Labiche, M.; Leino, M.; Mason, P.J.R.; McPeake, C.; O'Donnell, D.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Peura, P.; Rahkila, P.; Revill, J.P.; Ruotsalainen, P.; Sandzelius, M.; Saren, J.; Scholey, C.; Simpson, J.; Smith, J.F.; Smolen, M.; Sorri, J.; Stolze, S.; Thornthwaite, A.; Uusitalo, J.

Accepted for publication in Phys. Rev. C on 31st October 2019 Excited states have been identified in the very neutron-deficient N = Z + 3 nucleus Xe for the first time, using the Ni(Ni,αn) heavy-ion fusion-evaporation reaction. Gamma-ray transitions have been unambiguously assigned to Xe by correlation with the characteristic Xe→Te→Sn α-decay chain using the method of recoil-decay tagging. Inspection of γγ coincidence data has shown that five of the transitions form a rotational-like sequence. Excitation-energy systematics suggest that the sequence could be the favored signature partner of a band built on an h11/2 neutron. Aligned angular momenta of states in the band have been compared to analogous bands in neighboring xenon isotopes. The aligned angular momenta for the Xe band are constant over the range of observed rotational frequencies, suggesting that the first π(h11/2) 2 alignment is either delayed or absent. It is speculated that the alignment of h11/2 protons in the presence of neutrons in near-identical h11/2 orbitals may be affected by neutron-proton interactions, or by the onset of octupole correlations. PACS numbers: 23.20.Lv, 23.60.+e, 27.60.+j, 29.30.Kv Electronic address: John.F.Smith@uws.ac.uk Present address: Laboratory of Radiochemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland Present address: Department of Physics, Colorado School of Mines, Golden Colorado 80401, USA Present address: Helsinki Institute of Physics, P.O.Box 64, FI-00014 University of Helsinki, Finland Present address: Department of Physics, Ege Üniversitesi, Bornova, İzmir, Turkey Present address: Sodankylä Geophysical Observatory, University of Oulu, 90014 Oulu, Finland Present address: Argonne National Laboratory, Physics Division, Lemont, IL 60439, USA Present address: Division of Cancer Sciences, School of Medical Sciences, University of Manchester, Manch-

An analysis technique has been developed in order to mitigate energy summing due to sequential short-lived alpha decays from nuclei implanted into a silicon detector. Using this technique, alpha-decay spectroscopy of the N = 130 isotones Ra-218 (Z = 88) and Th-220 (Z = 90) has been performed. The energies of the alpha particles emitted in the Ra-218 -> Rn-214 and Th-220 -> Ra-216 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 Ra-218 and Th-220 have been measured to be 25.99(10) mu s and 10.4(4) mu s, respectively. The half-lives of the ground states of the alpha-decay daughters, Rn-214 and Ra-216, have been measured to be 259(3) ns and 161(11) ns, respectively. Fine structure in the alpha decay of Ra-218 has been observed for the first time, populating the 695-keV 2(1)(+) state in Rn-214. The fine-structure a decay has an alpha-particle energy of 7715(40) keV and branching ratio b(alpha) = 0.123(11)%.

Parr, E.; Page, R.D.; Joss, D.T.; Ali, F.A.; Auranen, K.; Capponi, L.; Grahn, T.; Greenlees, P.T.; Henderson, J.; Herzan, A.; Jakobsson, U.; Julin, R.; Juutinen, S.; Konki, J.; Labiche, M.; Leino, M.; Mason, P.J.R.; McPeake, C.; O'Donnell, D.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Peura, P.; Rahkila, P.; Revill, J.P.; Ruotsalainen, P.; Sandzelius, M.; Saren, J.; Scholey, C.; Simpson, J.; Smith, J.F.; Smolen, M.; Sorri, J.; Stolze, S.; Thornthwaite, A.; Uusitalo, J.

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 218 Ra ( Z = 88) and 220 Th ( Z = 90) has been performed. The energies of the α particles emitted in the 218 Ra → 214 Rn and 220 Th → 216 Ra 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 218 Ra and 220 Th have been measured to be 25.99(10) μ s and 10.4(4) μ s, respectively. The half-lives of the ground states of the α -decay daughters, 214 Rn and 216 Ra, have been measured to be 259(3) ns and 161(11) ns, respectively. Fine structure in the α decay of 218 Ra has been observed for the first time, populating the 695-keV 2 + 1 state in 214 Rn. The fine-structure α decay has an α -particle energy of 7715(40) keV and branching ratio b α = 0 . 123(11)%.

Fine structure in the a decay of high-spin isomers in Lu-155( 25/2(-)) and Hf-156(8(+))has been studied for the first time using alpha gamma- coincidence analysis. Three new a decays from Lu-155(25/2(-)) and two from Hf-156(8(+)) have been identified, populating seniority s > 1 states in the N = 82 nuclei Tm-151 and Yb-152, respectively. The reduced hindrance factors of the a decays support the previous configuration assignments of the populated states. This is the first observation of states with excitation energy greater than 1.5 MeV being populated following a decay in nuclei outside of the Pb-208 region.

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 ...

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.

B. Sayğı, 2 D. T. Joss, R. D. Page, T. Grahn, G. Alharshan, K. Auranen, T. Bäck, S. Boening, T. Braunroth, R. J. Carroll, B. Cederwall, D. M. Cullen, A. Dewald, M. Doncel, L. Donosa, M.C. Drummond, F. Ertugral, S. Ertürk, C. Fransen, P. T. Greenlees, M. Hackstein, K. Hauschild, A. Herzan, U. Jakobsson, P.M. Jones, R. Julin, S. Juutinen, J. Konki, T. Kröll, M. Labiche, A. Lopez-Martens, C.G. McPeake, F. Moradi, O. Möller, M. Mustafa, P. Nieminen, D. O’Donnell, J. Pakarinen, J. Partanen, P. Peura, M. Procter, P. Rahkila, W. Rother, P. Ruotsalainen, M. Sandzelius, J. Sarén, C. Scholey, J. Simpson, J. Sorri, S. Stolze, M.J. Taylor, A. Thornthwaite, and J. Uusitalo Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom. Department of Physics, Faculty of Science, Ege University, Bornova, Izmir, 35100, Turkey. University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014, University of Jyvaskyla, Finland. Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom. Department of Physics, Royal Institute of Technology, SE-10691, Stockholm, Sweden. Institut für Kernfysik, TU Darmstadt, Schlossgartenstr. 9, D-64289, Darmstadt, Germany. Institut für Kernphysik, Universität zu Köln, 50937 Köln, Germany. Nigde University, Science Faculty, Department of Physics, 51200 Nigde, Turkey STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, United Kingdom. Department of Physics, Oliver Lodge Laboratory, University of Liverpool,Liverpool, L69 7ZE, United Kingdom. Institut für Kernphysik, TU Darmstadt, 64289 Darmstadt, Germany. (Dated: May 8, 2017)

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.

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.

All material supplied via JYX is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. Direct observation of the Ba 114 →Xe 110 →Te 106 →Sn 102 triple α -decay chain using position and time correlations Capponi, L.; Smith, J. F.; Ruotsalainen, Panu; Scholey, Catherine; Rahkila, Panu; Auranen, Kalle; Bianco, L.; Boston, A. J.; Boston, H. C.; Cullen, D. M.; Derkx, X.; Drummond, M. C.; Grahn, Tuomas; Greenlees, Paul; Grocutt, L.; Hadinia, B.; Jakobsson, Ulrika; Joss, D. T.; Julin, Rauno; Juutinen, Sakari; Labiche, M.; Leach, K. G.; Leino, Matti; McPeake, C.; Mulholland, K. F.; Nieminen, Päivi; O'Donnell, D.; Paul, E. S.; Peura, Pauli; Sandzelius, Mikael; Sarén, Jan; Saygi, B.; Sorri, Juha; Stolze, Sanna; Thornthwaite, A.; Taylor, M. J.; Uusitalo, Juha

The triple α-decay chain Ba→Xe→Te→Sn has been directly observed for the first time, following the Ni(Ni,2n) reaction. Implantation of Ba nuclei into a double-sided silicon-strip detector has allowed their α decays to be correlated in position and time with the α decays of the daughter (Xe) and granddaughter (Te) nuclei. In total, 17 events have been assigned to the Ba→Xe→Te→Sn triple α-decay chain. The energy of the Ba α decay has been measured to be Eα=3480(20) keV, which is 70 keV higher than the previously measured value, and the half-life of Ba has been measured with improved accuracy, to be 380 −110 ms. A revised Q12C value of 19035(45) keV for Ba is presented. PACS numbers: 23.60.+e, 25.70.Gh, 27.60.+j Present address: ELI-NP, Horia Hulubei National Institute of Physics and Nuclear Engineering, 077125 Magurele, Romania Electronic address: John.F.Smith@uws.ac.uk Present address: TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada Present address: Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA Present address: Johannes Gutenberg-Universitt Mainz, 55099 Mainz, Germany Present address: Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki, Finland Present address: Helsinki Institute of Physics, P.O.Box 64, FI-00014 University of Helsinki, Finland