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International audience; Excited states in the extremely neutron-deficient nucleus Te107 have been identified from two separate experiments using the recoil-decay tagging technique. Two connected structures were observed on the basis of γγ-coincidence relations and tentatively assigned as built on the mixed-parentage νg7/2d5/2 and νh11/2 intruder configurations. The observed structures were compared with large-scale shell-model calculations and total Routhian surface calculations. Collective behavior was discovered to persist in the νh11/2 band of Te107 which highlights the shape-polarizing effect of a single valence neutron occupying the h11/2 intruder orbit as the N=50 shell closure is approached.

Excited states in the extremely neutron-deficient nucleus 107Te have been identified from two separate experiments using the recoil-decay tagging technique. Two connected structures were observed on the basis of γγ-coincidence relations and tentatively assigned as built on the mixed-parentage νg7/2d5/2 and νh11/2 intruder configurations. The observed structures were compared with large-scale shell-model calculations and total Routhian surface calculations. Collective behavior was discovered to persist in the νh11/2 band of 107Te which highlights the shape-polarizing effect of a single valence neutron occupying the h11/2 intruder orbit as the N=50 shell closure is approached. peerReviewed

The mean lifetimes of the lowest energy 2+, 8+ and 9− states in 166Os have been measured using the recoil distance Doppler-shift method in conjunction with a selective recoil-decay tagging technique. These measurements extend studies into the most neutron-deficient mass region accessible to current experimental methods. The B(E2; 2+ → 0+) = 7(2) W.u. extracted from these measurements is markedly lower than those observed in the heavier even-mass Os isotopes. The 8+ and 9− states yield reduced transition probabilities that are consistent with single-particle transitions. While these values may indicate a departure from collective structure, the level scheme and the underlying nuclear configurations can also be interpreted in terms of a simple collective picture. This contrasting behaviour suggests an intriguing dichotomy in the description of heavy transitional nuclei. peerReviewed

Excited states in the extremely neutron-deficient nucleus Pt-172 were populated via Ru-96(Kr-78, 2p) and Mo-92(Kr-83, 3n) reactions. The level scheme has been extended up to an excitation energy of approximate to 5MeV and tentative spin-parity assignments up to I-pi = 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 negativeparity band. The lowestmember 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 Pt-172. 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.

The level scheme of the neutron-deficient nuclide 168Os has been extended and mean lifetimes of excited states have been measured by the recoil distance Doppler-shift method using the JUROGAM γ -ray spectrometer in conjunction with the IKP Koln plunger device. The ¨ 168Os γ rays were measured in delayed coincidence with recoiling fusion-evaporation residues detected at the focal plane of the RITU gas-filled separator. The ratio of reduced transition probabilities B(E2; 4+ 1 → 2+ 1 )/B(E2; 2+ 1 → 0+ 1 ) is measured to be 0.34(18), which is very unusual for collective band structures and cannot be reproduced by interacting boson model (IBM-2) calculations based on the SkM* energy-density functional. peerReviewed

Excited states in the neutron-deficient N=84 nuclide 155Lu have been populated by using the 102Pd(58Ni,αp) reaction. The 155Lu nuclei were separated by using the gas-filled recoil ion transport unit (RITU) separator and implanted into the Si detectors of the gamma recoil electron alpha tagging (GREAT) spectrometer. Prompt γ-ray emissions measured at the target position using the JUROGAM Ge detector array were assigned to 155Lu through correlations with α decays measured in GREAT. Structures feeding the (11/2−) and (25/2−)α-decaying states have been revised and extended. Shell-model calculations have been performed and are found to reproduce the excitation energies of several of the low-lying states observed to within an average of 71 keV. In particular, the seniority inversion of the 25/2− and 27/2− states is reproduced. peerReviewed

Excited states in the neutron-deficient odd-odd proton-unbound nuclide 158Ta have been investigated in two separate experiments. In the first experiment, 166Ir nuclei were produced in the reactions of 380 MeV 78Kr ions with an isotopically enriched 92Mo target. The α-decay chain of the 9+ state in 166Ir was analyzed. Fine structure in the α decay of the 9+ state in 162Re established a 66 keV difference in excitation energy between the lowest-lying 9+ and 10+ states in 158Ta. Higher-lying states in 158Ta were populated in the reactions of 255 MeV 58Ni ions with an isotopically enriched 102Pd target. Gamma-ray decay paths that populate, depopulate, and bypass a 19− isomeric state have been identified. The general features of the deduced level scheme are discussed and the prospects for observing proton emission branches from excited states are considered. peerReviewed

WOS: 000390177700005, The level scheme of the neutron-deficient nuclide Os-168 has been extended and mean lifetimes of excited states have been measured by the recoil distance Doppler-shift method using the JUROGAM gamma-ray spectrometer in conjunction with the IKP Koln plunger device. The 168Os. rays were measured in delayed coincidence with recoiling fusion-evaporation residues detected at the focal plane of the RITU gas-filled separator. The ratio of reduced transition probabilities B(E2; 4(1)(+)-> 2(1)(+))/B(E2; 2(1)(+)-> 0(1)(+)) is measured to be 0.34(18), which is very unusual for collective band structures and cannot be reproduced by interacting boson model (IBM-2) calculations based on the SkM* energy-density functional., EURONS (European Commission)European Commission Joint Research Centre [RII3-CT-2004-506065]; Academy of Finland under the Finnish Centre of Excellence ProgrammeAcademy of Finland [213503]; UK Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC); Academy of FinlandAcademy of Finland [131665, 111965, 209430]; FWO-VlaanderenFWO; InterUniversity Attraction Pole Programme, Belgian State Federal Office for Scientific, Technical and Cultural Affairs (IAP) [P7/12]; Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC) [ST/J000108/1, ST/G008671/1, ST/L005670/1, ST/G008620/1, ST/L005743/1, ST/L005794/1, ST/G008787/1, EP/E004385/1, ST/J000094/1, EP/C015266/1, ST/L005816/1, ST/L005689/1], This work has been supported through EURONS (European Commission Contract No. RII3-CT-2004-506065), the Academy of Finland under the Finnish Centre of Excellence Programme 2006-2011 (Nuclear and Accelerator Based Physics Contract No. 213503), and the UK Science and Technology Facilities Council. The UK/France (STFC/IN2P3) Loan Pool and GAMMAPOOL network are acknowledged for the EUROGAM detectors of JUROGAM. T.G., P.T.G., and C.S. acknowledge the support of the Academy of Finland, Contracts No. 131665, No. 111965, and No. 209430, respectively. Financial support (K.H.) from the "FWO-Vlaanderen" and the InterUniversity Attraction Pole Programme, Belgian State Federal Office for Scientific, Technical and Cultural Affairs (IAP Grant No. P7/12) is acknowledged.

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.

WOS: 000274002700018, Decay paths, half-lives, and excitation energies of the i(13/2) bandheads of the neutron-deficient nuclei Pt-171, Os-167, and W-163 have been established for the first time. Gamma-ray transitions, X-rays, and internal conversion electrons have been observed, allowing internal-conversion coefficients to be measured and B(M2) reduced transition probabilities to be extracted. These results elucidate the low-lying single-quasiparticle structures and give the energy level spacings between the nu f(7/2), nu h(9/2), and nu i(13/2) quasineutron states for all three nuclei. Moreover, ground-state spin assignments have been made for the first time, along with the measurement of the alpha-decay branching ratio for Pt-171. The decay paths of the i(13/2) bandheads were followed by favored alpha decays, indicating that all three nuclei have the same I-pi = 7/2(-) ground state., Academy of Finland [44875, 213503]; Swedish Research Council; Goran Gustafsson Foundation; EU [HPRI-CT-1999-00044]; EXOTAG [HPRI-1999-CT-50017]; UK Engineering and Physical Sciences Research Council and Science; Technology Facilities Council [209430, 121110, 111965]; Slovak Research and Development Agency [APVV-20-006205]; Science and Technology Facilities Council [EP/C543157/1, EP/C015371/1, EP/C015266/1, ST/J000108/1, ST/G008671/1, ST/F012039/1, ST/G008620/1], This work has been supported by the Academy of Finland under the Finnish Centre of Excellence Programme (Project Nos. 44875 and 213503), the Swedish Research Council, the Goran Gustafsson Foundation, the EU FP5(HPRI-CT-1999-00044) and EXOTAG (HPRI-1999-CT-50017), through the EU-FP6-I3 project EURONS (RII3-CT-2004-506065), and the UK Engineering and Physical Sciences Research Council and Science and Technology Facilities Council. C. S. (209430), P.N. (121110), and P. T. G. (111965) acknowledge the support of the Academy of Finland; V. M., M. S., and I. G. D. acknowledge support from the EC Marie Curie Actions grant; V. M. acknowledges the Slovak Research and Development Agency (Contract No. APVV-20-006205); and E. I. and M. N. support from the JSPS Core-to-Core Program, International Research Network for Exotic Femto Systems. We thank the UK/France (STFC/IN2P3) Loan Pool and GAMMAPOOL European Spectroscopy Resource for the loan of the detectors for JUROGAM and GSI for the loan of the VEGA (1/4018/07) detectors.

WOS: 000272313000030, Excited states in Ta-163 have been identified for the first time using the Cd-106(Ni-60,3p) fusion evaporation reaction. gamma rays were detected using the JUROGAM gamma-ray spectrometer and recoil discrimination was achieved using the recoil ion transport unit (RITU) gas-filled separator in conjunction with the GREAT spectrometer situated at the focal plane of the RITU. The yrast states are assigned to a strongly coupled rotational band based on a pi h(11/2) configuration. This structure exhibits large signature splitting at low spins that disappears after the paired band crossing because of the alignment of a pair of i(13/2) neutrons. This effect is ascribed to triaxial shape changes induced by the core-polarizing properties of the deformation-aligned h(11/2) proton and the rotation-aligned i(13/2) neutrons. Two additional strongly coupled band structures have been established and are discussed in terms of octupole-vibrational and two-quasiparticle excitations built on the yrast structure. The experimental results are compared with predictions from cranked-shell-model and total-Routhian-surface calculations., Swedish Research Council; Goran Gustafsson Foundation; Academy of Finland under the Finnish Centre of Excellence Programme 2006-2011 [44875]; UK Science and Technology Facilities Council; European Union [HPRI-CT-1999-00044]; NordForsk [070315]; Turkish Atomic Energy Authority (TAEK) [DPT-04K120100-4]; Finnish Academy [209430-111965]; UK/France [EPSRC/IN2P3]; Science and Technology Facilities Council [ST/G008620/1, EP/C015266/1, ST/F012039/1, ST/G008671/1, EP/C015371/1, ST/J000108/1, EP/C543157/1], The authors thank the crew at the Accelerator Laboratory at the University of Jyvraskyla for their excellent technical support. Further support for this work has been provided by the Swedish Research Council, the Goran Gustafsson Foundation, the Academy of Finland under the Finnish Centre of Excellence Programme 2006-2011 (Project No. 44875, Nuclear and Condensed Matter Physics Programme at JYFL), the UK Science and Technology Facilities Council and the European Union Fifth Framework Programme "Improving Human Potential-Access to Research Infrastructure" (Contract No. HPRI-CT-1999-00044), the Nordic Infrastructure support by NordForsk (Project 070315), and the Turkish Atomic Energy Authority (TAEK) under Project No. DPT-04K120100-4. C. S. and P. T. G. acknowledge support from the Finnish Academy (Contract No. 209430-111965). We also thank the UK/France (EPSRC/IN2P3) Detector Loan Pool and the EUROBALL owners committee (gamma-pool network) for the loan of the EUROGAM detectors of JUROGAM and GSI for the loan of two additional VEGA clover detectors.

Excited states in the neutron-deficient isotopes 163Os and 165Os were identified using the JUROGAM and GREAT spectrometers in conjunction with the RITU gas-filled separator. The 163Os and 165Os nuclei were populated via the 106Cd(60Ni,3n) and 92Mo(78Kr,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 νf7/2 and νh9/2 orbitals. peerReviewed

Isomeric states in the semimagic 128-130Sn isotopes were populated in the fragmentation of a Xe136 beam on a Be9 target at an energy of 750 A•MeV. The decay of an isomeric state in Sn128 at an excitation energy of 4098 keV has been observed. Its half live has been determined to be T 1/2=220(30) ns from the time distributions of the delayed γ rays emitted in its decay. γγ coincidence relations were analyzed in order to establish the decay pattern of the newly established state toward the known (7-) and (10+) isomers at excitation energies of 2092 and 2492 keV, respectively. Based on a comparison with results of state-of-the-art shell-model calculations the new isomeric state is proposed to have the νh11/2-3d3/2-1 configuration with the four neutron holes in Sn132 maximally aligned to a total spin of Iπ=15-. © 2011 American Physical Society., We acknowledge financial support from the Spanish Ministerio de Ciencia e Innovacion under Contracts No. ´ FPA2007-66069 and No. FPA2009-13377-C02-02, the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007- 00042), the German Federal Ministry of Education and Research (06KY205I), the Swedish Science Council, STFC/EPSRC (UK), the Polish Ministry of Science and Higher Education (N N202 309135), and the EU Access to Large Scale Facilities Programme (EURONS, EU Contract No. 506065).

The neutron-deficient nucleus At199 has been studied through γ-ray and electron spectroscopy, using the recoil-decay tagging technique. Two experiments were conducted, using a gas-filled recoil separator with a focal-plane spectrometer alone and together with a germanium-detector array at the target position. The resulting level scheme for At199 includes a new isomer with a half-life of 0.80(5) μs and a spin and parity of (29/2+). The 13/2+ isomer, which de-excites via an M2 transition to the 9/2− ground state, was measured to have a half-life of 70(20) ns. Our earlier version of the level scheme for At197 has been updated as well. peerReviewed

The gamma decay of excited states in the waiting-point nucleus Cd-130(82) has been observed for the first time. An 8(+) two-quasiparticle isomer has been populated both in the fragmentation of a Xe-136 beam as well as in projectile fission of U-238, making Cd-130 the most neutron-rich N=82 isotone for which information about excited states is available. The results, interpreted using state-of-the-art nuclear shell-model calculations, show no evidence of an N=82 shell quenching at Z=48. They allow us to follow nuclear isomerism throughout a full major neutron shell from Cd-98(50) to Cd-130(82) and reveal, in comparison with Ni-76(48) one major proton shell below, an apparently abnormal scaling of nuclear two-body interactions.

The gamma decay of excited states in the waiting-point nucleus (130)Cd(82) has been observed for the first time. An 8(+) two-quasiparticle isomer has been populated both in the fragmentation of a (136)Xe beam as well as in projectile fission of 238U, making (130)Cd the most neutron-rich N = 82 isotone for which information about excited states is available. The results, interpreted using state-of-the-art nuclear shell-model calculations, show no evidence of an N = 82 shell quenching at Z = 48. They allow us to follow nuclear isomerism throughout a full major neutron shell from (98)Cd(50) to (130)Cd(82) and reveal, in comparison with (76)Ni(48) one major proton shell below, an apparently abnormal scaling of nuclear two-body interactions.

Low-spin structures in 86,88Mo were populated using the 58Ni(36Ar, x alpha yp) heavy-ion fusion-evaporation reaction at a beam energy of 111 MeV. Charged particles and gamma rays were emitted in the reactions and detected by the DIAMANT CsI ball and the EXOGAM Ge array, respectively. In addition to the previously reported low-to-medium spin states in these nuclei, new low-spin structures were observed. Angular correlation and linear polarization measurements were performed in order to unambiguously determine the spins and parities of intensely populated states in 88Mo. Quasiparticle Random Phase Approximation (QRPA) calculations were performed for the first and second excited 2+ states in 86Mo and 88Mo. The results are in qualitative agreement with the experimental results, supporting a collective interpretation of the low-spin states for these transitional nuclei.

Two separate experiments using the Differential Decay Curve Method have been performed to extract mean lifetimes of excited states in 106Cd. The medium-spin states of interest were populated by the 98Mo( 12C, 4n) 106Cd reaction performed at the Wright Nuclear Structure Lab., Yale University. From this experiment, two isomeric state mean lifetimes have been deduced. The low-lying states were populated by the 96Mo(13C, 3n)106Cd reaction performed at the Institut für Kernphysik, Universität zu Köln. The mean lifetime of the Iπ = 21+ state was deduced, tentatively, as 16.4(9) ps. This value differs from the previously accepted literature value from Coulomb excitation of 10.43(9) ps.

Picosecond lifetimes of medium spin states in Lu-165 were measured for the first time. The reaction used to populate the nucleus of interest was La-139(Si-30,4n)Lu-165 at a beam energy of 135 MeV. The beam was provided by the XTU-tandem accelerator of Laboratori Nazionali di Legnaro, Italy. By using the differential decay curve method, lifetimes of 19 states in four different rotational bands were obtained. Therefrom the B(E2) values and the transitional quadrupole moments were deduced. The obtained Q(t) for the different bands are compared with total Routhian surface (TRS) calculations and particle-rotor-model calculations. The TRS calculations predict different axial symmetric shapes for the bands built on the 9/2(-)[514], 9/2(+)[404], and 1/2(-)[541] configurations, with a gamma softness for the 9/2(-)[514] configuration. This band has also been studied using the particle-rotor model, the results of which, however, are consistent with a triaxial shape with a gamma value of -15(p).