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6 pags., 4 figs., 2 tabs., The change of the shell structure in atomic nuclei, so-called “nuclear shell evolution”, occurs due to changes of major configurations through particle-hole excitations inside one nucleus, as well as due to variation of the number of constituent protons or neutrons. We have investigated how the shell evolution affects Gamow-Teller (GT) transitions that dominate the β decay in the region below 132Sn using the newly obtained experimental data on a long-lived isomer in 127Ag. The T1/2=67.5(9) ms isomer has been identified with a spin and parity of (27/2+) at an excitation energy of 1942−20+14 keV, and found to decay via an internal transition of an E3 character, which competes with the dominant β-decay branches towards the high-spin states in 127Cd. The underlying mechanism of a strong GT transition from the 127Ag isomer is discussed in terms of configuration-dependent optimization of the effective single-particle energies in the framework of a shell-model approach., Part of the WAS3ABi was supported by the Rare Isotope Science Project which is funded by MSIP and NRF of Korea. This work was supported by the Priority Centers Research Program in Korea (2009-0093817), OTKA contract number K100835, the U.S. DOE, Office of Nuclear Physics (Contract No. DE-AC02-06CH11357), NRF2016R1A5A1013277 and NRF-2013M7A1A1075764, the Spanish Ministerio de Economía y Competitividad under contract FPA2017- 84756-C4-2-P, the European Commission through the Marie Curie Actions call FP7-PEOPLE-2011-IEF (Contract No. 300096), German BMBF under Contract No: 05P12PKFNE, JSPS KAKENHI Grant No. 24740188 and 25247045, the National Natural Science Foundation of China (Nos. 11505302, 11575112, 11775316), the National Key Program for S&T Research and Development (No. 2016YFA0400501), and STFC (UK).

The structure of excited states in the neutron-rich nucleus 31 Mg, which is in the region of the “island of inversion” associated with the neutron magic number N = 20 , is studied by β – γ spectroscopy of spin-polarized 31 Na. Among the 31 Mg levels below the one neutron separation energy of 2.3 MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic β decay. Two rotational bands with K π = 1 / 2 + and 1 / 2 − are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). It is found that various nuclear structures coexist in the low excitation energy region in 31 Mg.

Physics letters / B 762, 404 - 408 (2016). doi:10.1016/j.physletb.2016.09.058, Published by North-Holland Publ., Amsterdam

The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N=82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in Pd and Pd studied using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity U beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2 ) and (19/2 ) in Pd and Pd, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus Sn.

A. Jungclaus et al. -- 6 pags., 5 figs., 2 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0, A new high-spin isomer in the neutron-rich nucleus Cd was populated in the projectile fission of a U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T=6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15). The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus Cd. In the present experiment no evidence was found for the decay of a 18 E6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in the 0h and the 0g orbit, respectively, which is predicted to exist by the shell model., We thank the staff of the RIKEN Nishina Center accelerator complex for providing stable beams with high intensities to the experiment. We acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. This work was supported by the Spanish Ministerio de Ciencia e Innovación under contract FPA2011-29854-C04 and the Spanish Ministerio de Economía y Competitividad under contract FPA2014-57196-C5-4-P, the Generalitat Valenciana (Spain) under grant PROMETEO/2010/101, the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (NRF-2014S1A2A2028636, 2016K1A3A7A09005579, 2016R1A5A1013277), the Priority Centers Research Program in Korea (2009-0093817), OTKA contract number K-100835, JSPS KAKENHI (Grant No. 25247045), the European Commission through the Marie Curie Actions call FP7-PEOPLE-2011-IEF under Contract No. 300096, the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357, the STFC (UK), the “RIKEN foreign research program”, the German BMBF (No. 05P12RDCIA, 05P12RDNUP and 05P12PKFNE), HIC for FAIR, the DFG cluster of excellence “Origin and Structure of the Universe” and DFG (Contract No. KR2326/2-1).

The decay of a new four-quasiparticle isomeric state in 160Sm has been observed using γ-ray spectroscopy at the RIBF, RIKEN. The four-quasiparticle state is assigned a 2 π ⊗ 2 ν π 5 2 − [ 532 ] , π 5 2 + [ 413 ] , ν 5 2 − [ 523 ] , ν 7 2 + [ 633 ] configuration. The half-life of this ( 11 + ) state is measured to be 1.8(4) μs. The ( 11 + ) isomer decays into a rotational band structure, based on a ( 6 − ) ν 5 2 − [ 523 ] ⊗ ν 7 2 + [ 633 ] bandhead, consistent with the g K − g R values. This decays to a ( 5 − ) two-proton quasiparticle state, which in turn decays to the ground state band. Potential energy surface and blocked-BCS calculations were performed in the deformed midshell region around 160Sm. They reveal a significant influence from β 6 deformation and that 160Sm is the best candidate for the lightest four-quasiparticle K isomer to exist in this region. The relationship between reduced hindrance and isomer excitation energy for E1 transitions from multiquasiparticle states is considered with the new data from 160Sm. The E1 data are found to agree with the existing relationship for E2 transitions.

The first fast-timing measurements from nuclides produced via the in-flight fission mechanism are reported. The lifetimes of the first 2+states in 104,106Zr nuclei have been measured via β-delayed γ-ray timing of stopped radioactive isotope beams. An improved precision for the lifetime of the 2+1state in 104Zr was obtained, τ(2+1) =2.90+25−20ns, as well as a first measurement of the 2+1state in 106Zr, τ(2+1) =2.60+20−15ns, with corresponding reduced transition probabilities of B(E2; 2+1→0+g.s.) =0.39(2)e2b2and 0.31(1)e2b2, respectively. Comparisons of the extracted ground-state deformations, β2=0.39(1)(104Zr) and β2=0.36(1)(106Zr) with model calculations indicate a persistence of prolate deformation. The data show that 104Zr is the most deformed of the neutron-rich Zr isotopes measured so far.

The neutron-rich dysprosium isotopes ¹⁶⁸Dy₁₀₂ and ¹⁶⁹Dy₁₀₃ have been investigated using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity uranium beam in conjunction with isotope separation through the BigRIPS separator at RIBF in RIKEN Nishina Center. For ¹⁶⁸Dy, a previously unreported isomer with a half-life of 0.57(7) μs has been identified at an excitation energy of 1378 keV, and its presence affirmed independently using γ-γ-γ coincidence data taken with Gammasphere via two-proton transfer from an enriched ¹⁷⁰Er target performed at Argonne National Laboratory. This isomer is assigned Jπ = Kπ = (4⁻) based on the measured transition strengths, decay patterns, and the energy systematics for two-quasiparticle states in N = 102 isotones. The underlying mechanism of two-quasiparticle excitations in the doubly midshell region is discussed in comparison with the deformed QRPA and multi-quasiparticle calculations. In ¹⁶⁹Dy, the B(E2) value for the transition de-exciting the previously unreported Kπ = (1/2⁻) isomeric state at 166 keV to the Kπ = (5/2⁻) ground state is approximately two orders of magnitude larger than the E2 strength for the corresponding isomeric-decay transition in the N = 103 isotone ¹⁷³Yb, suggesting the presence of a significant γ-vibrational admixture with a dominant neutron one-quasiparticle component in the isomeric state.

The decay of an isomeric state in the neutron-rich nucleus 129 Cd has been observed via the detection of internal conversion and Compton electrons providing first experimental information on excited states in this nucleus. The isomer was populated in the projectile fission of a 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. From the measured yields of γ -rays and internal conversion electrons, a multipolarity of E 3 was tentatively assigned to the isomeric transition. A half-life of T 1 / 2 = 3.6 ( 2 ) ms was determined for the new state which was assigned a spin of ( 21 / 2 + ) , based on a comparison to shell model calculations performed using state-of-the-art realistic effective interactions.

5 pags., 3 figs., 2 tabs., Neutron-rich nuclei in the vicinity of Ni78 were produced using a U238 beam at the RIKEN Radioactive Isotope Beam Factory. The particle-identification plot for the in-flight fission fragments highlights the first observation of eight new isotopes: Mn73, Fe76, Co77,78, Ni80,81,82, and Cu83. Although the β-decay half-lives of Co77 and Ni80 were recently reported by Xu [Phys. Rev. Lett. 113, 032505 (2014)]PRLTAO0031-900710.1103/PhysRevLett.113.032505 using data from the same experiment, the current work provides the first direct, quantitative evidence for the existence of these isotopes. The experimental production cross sections are reproduced in a satisfactory manner by theoretical predictions. An odd-even staggering of the cross sections was observed, and the effect appears to become more pronounced for the most exotic nuclei that were investigated. The staggering effect was interpreted as an increase of the neutron-evaporation probability for odd-N isotopes, owing to the decrease of the neutron-separation energy, Sn. The predicted cross section for Ni80 is significantly overestimated, which may be related to a weak binding of the neutron pair above the N=50 shell closure., This work was supported by JSPS KAKENHI (25247045, 25800130), the Spanish Ministerio de Ciencia e Innovación under Contracts No. FPA2009-13377-C02 and No. FPA2011- 29854-C04, OTKA Contract No. K-100835, U.S. DOE Contract No. DE-FG02-91ER40609, and the Priority Centers Research Program in Korea (2009-0093817).

Spin-polarized radioactive nuclear beams at TRIUMF enable a new spectroscopic method which efficiently assigns spins and parities of the daughter levels by taking advantage of the asymmetric β-decay of the polarized parent nucleus. This method was successfully applied to structure studies of 29Mg and 30Mg in connection with the physics of the “island of inversion”. In 29Mg, two low-lying levels with intruder configuration were assigned. In 30Mg, coexistence of spherical shape, prolate shape and γ-collectivity was strongly suggested.

In the EURICA campaign aimed at exploration of the $^{78}\mathrm{Ni}$ region, an isomeric state of $^{76}\mathrm{Co}$ has been observed via $\ensuremath{\gamma}$-ray spectroscopy. The nuclei were produced by in-flight fission of a $^{238}\mathrm{U}$ beam at the Radioactive Isotope-Beam Factory. Two coincident $\ensuremath{\gamma}$ rays of $192.02(30)$ and $446.4(7)$ keV from the decay of a ${t}_{1/2}=2.96{(}_{25}^{29})\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ isomeric state of $^{76}\mathrm{Co}$ have been observed. The decay of the isomer was assigned to an $E1$ transition with a reduced transition probability of $B(E1;{3}^{+}\ensuremath{\rightarrow}{2}^{\ensuremath{-}})=1.79(16)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ W.u. A $\ensuremath{\beta}$-decaying state with spin-parity ${1}^{\ensuremath{-}}$ and a half-life of $16(4)$ ms was also observed in the data, and the known state with a half-life of $22{(}_{5}^{7})$ ms was assigned to have a spin-parity of ${8}^{\ensuremath{-}}$. Furthermore, the isomer of $^{76}\mathrm{Ni}$ has been remeasured to $547.8(33)$ ns giving a $B(E2;{8}^{+}\ensuremath{\rightarrow}{6}^{+})$ value of $0.786(5)$ W.u. A new excited state at $2994.6(5)$ keV, decaying via a $\ensuremath{\gamma}$ ray of 2004.5(4) keV, has also been observed. This is in agreement with either of the predicted ${0}_{2}^{+}$ or ${2}_{2}^{+}$ states. These results are discussed in terms of the shell model and the interaction of the $\ensuremath{\nu}{p}_{1/2}$ and $\ensuremath{\pi}{f}_{7/2}$ orbitals.

The level structures of 28 Mg and 29 Mg have been investigated by the β-decay of spin-polarized28 Na and 29 Na at ISAC, TRIUMF. The detailed β-γ and γ-γ coincidence measurements were performed. New γ rays and β transitions were observed both in 28 Mg and 29 Mg . We have succeeded in assigning spins and parities of many levels in 28 Mg and 29 Mg . Comparison with shell model calculations using USD Hamiltonian suggest that the structure of 28 Mg and 29 Mg are well explained in the sd-shell configurations, except for two levels at 1.095 and 1.430 MeV in 29 Mg . This suggests negative parity assignments for these levels. The evolution of sd-pf shell is discussed.

Experiments based on the isomer-spectroscopy method were performed using the secondary beam line at RCNP, Osaka University. Recently, a new γ-ray spectroscopy method was established using fusion reaction induced by low-energy RI beam. This method enables us to study high-spin states of nuclei in wider mass region where it is difficult to populate them by using the combination of stable beams and stable targets. This method works well although low production of nuclei, because (1) the combination of beams and targets can be selected with large-reaction cross section and (2) high-S/N measurement can be performed by the event-by-event detection to select the events correlated with RI beam, which reduces background γ rays, competing with γ rays emitted from fusion products. As the first step, high-spin states of 142 Pr were studied using fusion reaction induced by low-energy 17 N RI beam. Large cross section was obtained by the 130 Te (17 N ,5 n ) reaction with 4.9 MeV/u 17 N beam. Event selection, which was carried out by the event-by-event detection with low-beam intensity of 2×104 pps, enables high-S/N measurement.

The neturon rich nucleus 13B was studied via the proton transfer reaction 4He(12Be,13B \gamma) at 50AMeV. The known 4.83-MeV excited state was strongly populated and its spin and parity were assigned to 1/2+ by comparing the angular differential cross section data with DWBA calculations. This low-lying 1/2+ state is interpreted as a proton intruder state and indicates a deformation of the nucleus., Comment: 16 pages, 3 figures

Mean lifetime tau of the isomeric O-2(+) state in Be-12 has been determined by measuring decay spectra of delayed y-rays from stopped Be-12 2 nuclei produced by the projectile fragmentation of O-18 at 100 A MeV. A consistent value of tau = 331 +/- 12 ns was obtained from the time spectra of the E2 gamma decay to the 2(1)(+) state and the positron annihilation following the E0 decay to the ground state. Based on the observed branching ratio between the E2 and E0 decays, transition strengths of the two decay modes were deduced to be B(E2; O-2(+) -> 2(1)(+)) = 7.0 +/- 0.6 e(2) fm(4) and 2 1 1 (O-2(+) Sigma(i) e(i) r(i)(2) O-1(+)), = 0.87 +/- 0.03 e fM(2), respectively. (C) 2007 Elsevier B.V. All rights reserved.

Single-particle properties of low-lying resonance levels in 14O have been studied efficiently by utilizing a technique of proton elastic resonance scattering with a 13N secondary beam and a thick proton target. The excitation functions for the N 13 + p elastic scattering were measured over a wide energy range of E CM = 0.4 – 3.3 MeV and fitted with an R-matrix calculation. A clear assignment of J π = 2 − has been made for the level at E x = 6.767 ( 11 ) MeV in 14O for the first time. The excitation functions show a signature of a new 0 − level at E x = 5.71 ( 2 ) MeV with Γ = 400 ( 100 ) keV . The excitation energies and widths of the 14O levels are discussed in conjunction with the spectroscopic structure of A = 14 nuclei with T = 1 .

Shell-model calculations are performed for even-even, odd-mass, and doubly-odd nuclei of Sn, Sb, Te, I, Xe, Cs, and Ba isotopes around mass 130 using the single-particle space made up of valence nucleons occupying the $0{g}_{7/2},\phantom{\rule{0.16em}{0ex}}1{d}_{5/2},\phantom{\rule{0.16em}{0ex}}2{s}_{1/2},\phantom{\rule{0.16em}{0ex}}0{h}_{11/2}$, and $1{d}_{3/2}$ orbitals. The calculated energies and electromagnetic transitions are compared with the experimental data. In addition, several typical isomers in this region are investigated.

We report new data on the $^{136}\mathrm{Sb}\phantom{\rule{4pt}{0ex}}{6}^{\ensuremath{-}}$ yrast isomer with ${T}_{1/2}=489(40) \mathrm{ns}$ and $\ensuremath{\pi}{g}_{7/2}^{1}\ifmmode\times\else\texttimes\fi{}\ensuremath{\nu}{f}_{7/2}^{3}$ configuration, populated in the projectile fission of $^{238}\mathrm{U}$ on a $^{9}\mathrm{Be}$ target. The analysis confirms the lifetime, providing a good accuracy measurement. In addition, the decay of the isomer to the ground state is newly suggested. Our result for the isomeric decay scheme is in a good agreement with shell-model calculations.

High-spin states in the odd-odd nucleus La136, which is located close to the β-stability line, have been investigated in the radioactive-beam-induced fusion-evaporation reaction Sn124(N17,5n). The use of the radioactive beam enabled a highly sensitive and successful search for a new isomer [14+,T1/2=187(27) ns] in La136. In the A=130–140 mass region, no such long-lived isomer has been observed at high spin in odd-odd nuclei. The La136 level scheme was revised, incorporating the 14+ isomer and six new levels. The results were compared with pair-truncated shell model (PTSM) calculations which successfully explain the level structure of the πh11/2⊗νh−111/2 bands in La132 and La134. The isomerism of the 14+ state was investigated also by a collective model, the cranked Nilsson-Strutinsky (CNS) model, which explains various high-spin structures in the medium-heavy mass region. It is suggested that a new type of collective structure is induced in the PTSM model by the increase of the number of πg7/2 pairs, and/or in the CNS model by the configuration change associated with the shape change in La136.

In the first half of the paper, the nuclear astrophysics activities in Japan, especially in experimental studies are briefly overviewed. A variety of beams have been developed and used for nuclear astrophysics experiments in Japan. The activities include the RI beam facilities at low energies by the in-flight method at the Center for Nuclear Study (CNS), University of Tokyo and by the ISOL-based method at the JAERI tandem facility, and the RI beam facility at intermediate energies at RIKEN. Other activities include a study of the 12C(α, γ)16O reaction exclusively at the tandem accelerator at the Kyushu University, and studies at the neutron facility at Tokyo Institute of Technology and at the photon facility at AIST (Sanso-ken). Research opportunities in the future at RIBF, J-PARC, and SPRING8 are also discussed. A discussion on the research activities at CNS has been specifically extended in the latter half, including various possibilities in collaboration at the RI beam factory at RIKEN

The g-factor of the 27− isomer state of 152Dy has been measured using the Time- Integral Perturbed Angular Distribution (TIPAD) method. The high-spin states of 152Dy have been populated by 141Pr(16O,p4n)152Dy reaction at E = 115 MeV from the AVF cyclotron at CYRIC. The paramagnetic correction factor of Dy ions in Pr has been determined to be 4.2(5) by the Time- Differential Perturbed Angular Distribution (TDPAD) measurement of the 21− state of 152Dy. As a result, the g-factor of the 27− isomer state of 152Dy has been obtained to be +0.09(5). This shows the smaller value than the expected one of +0.39 deduced from a fully aligned configuration of π(h 11 2/2 ) ⊗ v(f 7 2/2 h 9/2 i 13/2).

With using low-energy RI beams from an in-flight RIB separator, CRIB, the most crucial stellar reaction 14 O( α ,p) 17 F for the onset of the high-temperature rp-process was directly investigated and the transitions through the states at around 6.2 MeV in 18 Ne were first observed, confirming the importance predicted before. The ( α ,p) reaction leading to the first excited state in 17 F was also found to have a large contribution. A proton resonance search experiment of 23 Mg + p was also discussed, which is a part of our series of resonance search studies relevant to the early stage of the rp-process.

The high-spin states of 93Mo have been studied by a 82Se( 16O, 5n) 93Mo reaction at a beam energy of 100 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-t, γ-γ-t coincidences, γ-ray angular distributions and γ-ray linear polarizations were performed. The high-spin isomer was found as a (39/2-) state at about 9.7 MeV. The near-yrast states in 93Mo were interpreted using the weak-coupling picture of a d5/2 neutron to a neutron magic core nucleus 92Mo.

The stellar reaction 14 O( α ,p) 1 7F, that critically determines the onset of the high-temperature rp-process, has been studied through a direct measurement with a low-energy radioactive 14 O beam and a gaseous helium target cooled down to 30 K. The reaction cross section was measured directly by means of a thick target technique in the energy range of E c.m. ( 14 O+ α ) = 0.8-3.8 MeV. The 14 O( α ,p) 17 F * reaction leading to the first excited state in 17 F was clearly observed for the first time, suggesting an increase of about 50% for the stellar reaction rate through resonance at around 7.1 MeV in 18 Ne.

A new high-spin isomer in 150Dy has been observed at an excitation energy of 10.3 MeV by combining the inverse-kinematic reaction induced by a pulsed beam of 132Xe and the $\gamma$ -ray recoil-shadow technique. The half-life of this isomeric state has been determined to be $T_{1/2} = 1.6 \pm 0.6$ ns using the conventional centroid-shift method with the 141Pr(16O, p6n)150Dy reaction at 165 MeV. The mechanism producing high-spin isomers in N = 83,84 isotones is qualitatively discussed in terms of the difference of the neutron particle-hole configuration between the high-spin isomer and the lower-lying state.

The ability to align liquid crystals to a substrate is a critical step in the liquid crystal display (LCD) manufacturing process with the industry standard technique employing a mechanical rubbing technique to accomplish this function. However, mechanical rubbing can result in debris generation contaminating not only the substrate being processed but also the clean room housing the equipment. As such, post-cleaning of the display panels is required to remove the debris from the surface in addition to the physical isolation of the mechanical rubbing equipment within the clean room environment introducing considerable time and expense. In addition, uneven wear of the mechanical roller during the rubbing process may result in localized defects that will not be observed until final inspection of a completely assembled display. We have developed and introduced into LCD manufacturing a non-contact alignment technique utilizing both diamond-like carbon (DLC) and a low energy ion beam (IB). The replacement of the polyimide alignment layer with DLC results in a completely dry processing technique for both the thin film deposition and alignment steps.

The first evidence for excited states in Ag-95 is presented. Ag-95 is the heaviest T-z = 1/2 nucleus for which gamma-rays have been identified. The reaction Ca-40(Ni-58, 1p2n)Ag-95 was used in the ...

A high-spin isomeric beam line has been constructed at RIKEN based on the inverse kinematics of fusion–evaporation reactions. The beam line provides high-spin isomers as secondary beams, whose intensity is more than 10 5 sec −1 . The characteristics and the present status of the beam line are described.

High-spin states of 155Gd were populated by using the 154Sm(α,3nγ)155Gd reaction at E α= 33 MeV. γ-γ coincidence, E γ singles, excitation function, and the DCO ratios were measured. we have identified three intermediate bands with ΔI= 2 feeding the positive yrast band. The bands are interpreted as such candidate bands that are mixed with the negative-parity ground state band. This observation can provide a plausible explanation for unusually large population of the positive-parity yrast band observed in a recent Coulomb excitation.

High spin states of 146Eu were studied by in-beam gamma ray spectroscopic techniques using 140Ce(10B,4n)146Eu and 139La(13C,6n)146Eu reactions. The level scheme was established up to 10MeV. A new high spin isomer with 10ns half life was found. Configurations of yrast states were understood by a weak coupling of f7/2 neutron to those of 145Eu.

The high-spin isomer in 151Er ( Ex = 10.3 MeV, T1/2 = 420 ns) has been studied by the 116Sn ( 40Ar , 5n) 151Er reaction at 197MeV. From the \( \gamma \gamma\) coincidence relations, a new transition with an energy of 1514keV was found. This finding requires the revision of the spin-parity assignment from previous 67/2- to 61/2+ or 65/2- . The 61/2+ assignment is the one which was predicted by the deformed independent particle model as an isomer with a large oblate deformation ( \( \beta\) = - 0.17) of the \(\ensuremath[\nu(f_{7/2}h_{9/2} i_{13/2}) \pi(h^4_{11/2})]_{61/2^+}\) configuration. The isomerism may be attributed to the sudden shape change of the isomer from the nearly spherical shape of the lower-spin yrast states to the oblate shape.

A recoil distance method was used to measure half-lives of the excited states of 145Sm. The reaction used was 139La(10B, 4n)145Sm. A plunger system was used. Half-lives were determined for two excited states for the first time. The yrast 27/2+ state was found to have a half-life of 1.1 ± 0.2 ns corresponding to the retardation of 3.1 × 10−4 comparing with the single particle estimate of M1. The excitation energy of this state was well reproduced by the shell model calculation having a mixed configuration of [π{h11/2(g7/2)−2 (d5/2)−1}10−, νf7/2] + [π{h11/2(g7/2)−1}9−,νh9/2]. Another retarded E1 transition was also found in a decay of a 21/2+ state. Its retardation was 1.6 × 10−4 comparing with the single particle value.

${}^{116}\mathrm{Ru}$ and ${}^{118}\mathrm{Ru}$ have been studied via $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin $J=6$ have been constructed. The results have been discussed in terms of the interacting boson model, the algebraic collective model, and total Routhian surfaces. We conclude that the very neutron-rich nuclei still show many features associated with triaxial $\ensuremath{\gamma}$-soft nuclei, represented by the O(6) symmetry, but are approaching a spherical structure, the U(5) symmetry, with increasing neutron number towards the $N=82$ shell closure. In ${}^{118}\text{Ru}$, hints of a shape transition in the ground state have been observed.

The 135La nucleus has been studied using the fusion-evaporation reaction 124Sn(17N,6n) induced by the 17N radioactive beam. The level scheme has been constructed from the γ-γ coincidence measurement with an array of 12 HPGe detectors, and the lifetimes of two previously known isomeric states has been deduced. The transitions and their intensities observed in the current work as well as the level scheme derived from them is in agreement with the results of a recently published work. However, our interpretation of the results differs significantly in terms of spin and parity assignments, thus solving various contradictions concerning the configurations of some of the bands discussed in the aforementioned work.

EURICA is a project at RIKEN Nishina Center aimed at studying a wide range of exotic nuclei through β-decay measurements and high-resolution γ-ray spectroscopy. The setup is located behind the BigRIPS fragment separator and the ZeroDegree spectrometer at the RIBF. EURICA consists of the HPGe cluster detectors from the previous Euroball and RISING projects, together with double-sided silicon-strip detectors for β-decay counting and lifetime measurements. In total, this setup provides us with the possibility to study several aspects of the exotic nuclei produced at the RIBF. © 2013 Elsevier B.V. All rights reserved.

A new experimental technique utilizing a high-spin isomer beam (HSIB) has been developed. The HSIB of 174Hf was produced by the 9Be(170Er, 5n)174Hf reaction in inverse kinematics. By using the HSIB, the Coulomb excitation of the Kπ = 8− isomer in 174Hf was measured. The γ-rays from the 9− level, which is the first excited state built on the isomer, were observed as well as the cascade γ-rays of the ground-state rotational band. From the measured γ-ray yield, a value of 2 ± 1 e2b2 was extracted for the B(E2: 8− → 9−). This is the first experiment of γ-ray spectroscopy by means of the HSIB-induced secondary reactions.

Theβ + decay of86Mo has been firstly investigated by means ofβγ spectroscopy. The86Mo nuclei were produced by fusion-evaporation reactions of54 Fe (35Cl, 1 p2n) and58Ni (32S,2p 2n) at beam energies of 103 and 120 MeV, respectively. Threeγ rays of 47.3, 49.8 and 187.0 keV were unambiguously identified to follow theβ + decay of86Mo by results ofXγ andβγ coincidence and cross-bombardment. A half life and a maximumβ +-ray energy of86Mo were determined to be 19.6±1.1 s and 3.9±0.4 MeV, respectively. A decay scheme of86Mo is proposed in this article. Furthermore, a decay of86Nb has been studied using the same combinations of projectiles and targets, and a newβ-decaying isomer86m Nb was observed with a half life of 56.3±8.3 s.

High-spin states in 82 Y have been studied by the 58 Ni( 28 Si,3pn) reaction at 128 MeV. Low-lying states were investigated by the same reaction but at a lower bombarding energy and the band heads of the high-spin sequences have been characterized. Four rotational bands forming two sets of signature partners were established. The yrast band was observed up to j π = 27 + and shows (large signature splitting, while a negative-parity yrare band, observed up to spin 22 shows a much smaller splitting. The yrast band structure was very similar to the g 9 2 proton band in 79 Rb.

The neutron-rich nucleus 110Mo has been investigated by means of γ-ray spectroscopy following the β-decay of 110Nb, produced using in-flight fission of a 238U beam at 345 MeV/nucleon at the RIBF facility. In addition to the ground-band members reported previously, spectroscopic information on the low-lying levels of the quasi-γ band built on the second 2 + state at 494 keV has been obtained for the first time. The experimental finding of the second 2 + state being lower than the yrast 4 + level suggests that axially-asymmetric γ softness is substantially enhanced in this nucleus. The experimental results are compared with model calculations based on the general Bohr Hamiltonian method. The systematics of the low-lying levels in even–even A ≈ 110 nuclei is discussed in comparison with that in the neutron-rich A ≈ 190 region, by introducing the quantity E S / E ( 2 1 + ) , E S = E ( 2 2 + ) − E ( 4 1 + ) , as a global signature of the structural evolution involving axial asymmetry.

The neutron deficient nucleus82Zr has been studied through the reaction58Ni(28Si, 2p 2n)82Zr with a calculated cross section of 0.3% of the total fusion cross section atE(28Si)=128 MeV. Gamma rays from excited states of82Zr were measured and identified using the NORDBALL escape-suppression array at the Niels Bohr Institute. Reaction channel selection was performed by use of neutron and charged particle detector arrays in conjunction with the germanium detectors. A rotational band in82Zr has been identified with spins up to 20 ħ by analysis of reaction channel selectedγ-γ coincidence matrices. Band crossings were identified at frequencies 0.57 and 0.69 MeV.

High-lying and high spin states of nuclei around N,Z=40 have studied using the ( 58 Ni + 28 Si) and ( 58 Ni + 32 S) reactions and NORDBALL Ge-Array equipped with a Silicon Ball for light charged particle detection. Simultaneously complementary experiment have been carried out using in-beam and β decay measurements to establish lifetimes and spin-party values of low-lying and ground states at Kyushu University. Some of results are reported.