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The shell closure at N= 32 has been investigated by a first spectroscopy of the N= 31 nucleus Ar 49 at the Radioactive Isotope Beam Factory. Using the Ar 50 (p, p n) reaction channel in inverse kinematics, Ar 50 projectiles at 217 MeV/nucleon impinged on a 150 mm long liquid hydrogen target, part of the MINOS device. Prompt deexcitation γ rays were measured with the NaI (Tl) array DALI 2+. Reaction products were analyzed with the SAMURAI spectrometer, which allowed the measurement of the momentum distributions and angular momentum transfer. Data were compared to state-of-the-art theoretical predictions, including shell-model, energy-density functional, and ab initio calculations. An onset of collectivity is suggested besides the spherical configuration typical of a closed shell nucleus, such as for Ca 52.

NUCLEAR REACTIONS 3 He (32 S, α) 31 S, E= 128 MeV; measured reaction products, Eγ, Iγ; deduced γ-ray energies, levels, T 1/2, resonances. Comparison with the shell-model code NuShellX calculations. Modern Markov chain Monte Carlo-based Bayesian statistical techniques. The Doppler Shift Lifetimes (DSL2) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility.

We report on a study of the α-decay fine structure and the associated E α− E γ correlations in the decays of Os 171, 172 and Ir 171, 172, 174. 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 Re 168 and W 167. The weak α-decay branch from the bandhead of the ν i 13/2 band in Os 171 observed in this work highlights an unusual competition between α, β, and electromagnetic decays from this isomeric state. The nucleus Os 171 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 Mo 92 (Kr 83, x p y n) 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 …

Isomeric states of the neutron-rich isotope 18973Ta116 were populated via fragmentation of a primary beam of 208Pb ions at 1 GeV/u impinging on a 9Be target at GSI, Darmstadt, Germany. The isotopes of interest were separated, identified and delivered to the DESPEC setup. Two isomers were deduced in 189Ta116 and their lifetimes were measured based on the γ-ray time distributions.

Direct lifetime measurements via γ–γ coincidences using the FATIMA fast-timing LaBr3(Ce) array were performed for the excited states below previously reported isomers. In the N = 50 semi-magic 96Pd nucleus, lifetimes below the I π = 8+ seniority isomer were addressed as a benchmark for further analysis. The results for the I π = 2+ and 4 + states confirm the published values. Increased accuracy for the lifetime value was achieved for the 4 + state.

S. Chen a, b, c,∗, F. Browne b, P. Doornenbal b, J. Lee a, A. Obertelli d, e, b, Y. Tsunoda f, T. Otsuka b, g, h, Y. Chazono i, G. Hagen n, j, JD Holt k, l, GR Jansen m, n, K. Ogata i, o, N. Shimizu f, Y. Utsuno h, f, K. Yoshida h, NL Achouri p, H. Baba b, D. Calvet e, F. Château e, N. Chiga b, A. Corsi e, ML Cortés b, A. Delbart e, J.-M. Gheller e, A. Giganon e, A. Gillibert e, C. Hilaire e, T. Isobe b, T. Kobayashi q, Y. Kubota b, f, V. Lapoux e, HN Liu e, d, r, T. Motobayashi b, I. Murray s, b, H. Otsu b, V. Panin b, N. Paul e, t, W. Rodriguez b, u, v, H. Sakurai b, g, M. Sasano b, D. Steppenbeck b, L. Stuhl f, w, x, YL Sun e, d, Y. Togano y, T. Uesaka b, K. Wimmer g, b, K. Yoneda b, O. Aktas r, T. Aumann d, z, LX Chung aa, F. Flavigny s, S. Franchoo s, I. Gasparic ab, d, b, R.-B. Gerst ac, J. Gibelin p, KI Hahn ad, x, D. Kim ad, b, x, T. Koiwai g, Y. Kondo ae, P. Koseoglou d, z, C. Lehr d, BD Linh aa, af, T. Lokotko a, M. MacCormick s, K. Moschner ac, T. Nakamura ae, SY Park ad, x, D. Rossi d, E. Sahin ag, P.-A. Söderström d, D. Sohler w, S. Takeuchi ae, H. Törnqvist d, z, V. Vaquero ah, V. Wagner d, S. Wang ai, V. Werner d, X. Xu a, H. Yamada ae, D. Yan ai, Z. Yang b, M. Yasuda ae, L. Zanetti d a Department of Physics, The University of Hong Kong, Pokfulam, Hong Kong b RIKEN Nishina Center, Wako, Saitama, Japan c School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China d Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany e IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, France f Center for Nuclear Study, University of Tokyo, RIKEN campus, Wako, Saitama, Japan g …

Gamma decays were observed in 56 Ca and 58 Ca following quasi-free one-proton knockout reactions from 57, 59 Sc beams at≈ 200 MeV/nucleon. For 56 Ca, a γ ray transition was measured to be 1456 (12) keV, while for 58 Ca an indication for a transition was observed at 1115 (34) keV. Both transitions were tentatively assigned as the 2 1+→ 0 gs+ decays, and were compared to results from ab initio and conventional shell-model approaches. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for 2 1+ level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the N= 34 shell. Its constituents, the 0 f 5/2 and 0 g 9/2 orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic 60 Ca and potentially …

Three three-quasiparticle isomers, one at an excitation energy of 2.3 MeV with T 1/2= 0.48 (4) μ s, and two shorter-lived with unknown half-lives at slightly lower energies have been identified in Nd 129 using the MARA+ JUROGAM 3 setup and the recoil tagging technique. All three isomers present decay patterns characteristic of high-K isomers. The known 6.7 s β-decaying isomer previously assigned to the 5/2+ level is now assigned to the new 7/2− ground state. A new low-spin 5/2+ isomeric state with a half-life of a few tens of nanoseconds has been identified, while a previously known 2.6 s β-decay activity was assigned to the band head of the ν 1/2+[411] band. The transitions depopulating the high-K isomers to low-lying states also establish the relative energies of three low-lying one-quasiparticle bands, leading to a new spin-parity assignment of 7/2− to the ground state of Nd 129. The partial half-lives of the …

The quantum tunneling and emission of a single constituent nucleon provide a beautifully simple and unique window into the complex properties of atomic nuclei at the extreme edge of nuclear existence. In particular, for odd-odd proton emitting nuclides, the associated decay energy and partial half-life can be used to probe the correlations between the valence neutrons and protons which have been theoretically predicted to favour a new type of nuclear superfluidity, isoscalar neutron-proton pairing, for which the experimental “smoking gun" remains elusive. In the present work, proton emission from the lanthanum isotope 11657La59, 23 neutrons away from the only stable isotope 13957La82, is reported. 116La nuclei were synthesised in the fusion-evaporation reaction 58Ni(64Zn, p5n)116La and identified via their proton radioactivity using the mass spectrometer MARA (Mass Analysing Recoil Apparatus) and the silicon detectors placed at its focal plane. Comparisons of the measured proton energy (Ep = 718 ± 9 keV) and half-life (T1/2 = 50 ± 22 ms) with values calculated using the Universal Decay Law approach indicate that the proton is emitted with an orbital angular momentum l = 2 and that its emission probability is enhanced relative to its closest, less exotic, odd-even lanthanum isotope (11757La60) while the proton-emission Q-value is lower. We propose this to be a possible signature for the presence of strong neutron-proton pair correlations in this exotic, neutron deficient system. The observations of γ decays from isomeric states in 116La and 117La are also reported.

Three new negative-parity bands have been identified in Ba 120, two of them forming a strongly coupled band. The previously known negative-parity band is significantly extended to high spin, while the lower part of the yrare positive-parity band has been modified. From the analysis of the band properties and comparison with the neighboring nuclei a coherent description of all bands is achieved. In particular, a simple explanation of the evolution of the positive-parity bands at high spin is proposed, including the possible occupation of the ν f 7/2 [541] 1/2− intruder orbital. Cranked Nilsson-Strutinsky calculations reveal similar quadrupole deformations but different triaxiality of the bands, while particle number conserving cranked shell model calculations qualitatively reproduce the experimental data and support the assigned configurations. The new measured ratios of reduced transition probabilities B (E 1)/B (E 2 …

The quantum tunneling and emission of a single constituent nucleon provide a beautifully simple and unique window into the complex properties of atomic nuclei at the extreme edge of nuclear existence. In particular, for odd-odd proton emitting nuclides, the associated decay energy and partial half-life can be used to probe the correlations between the valence neutrons and protons which have been theoretically predicted to favour a new type of nuclear superfluidity, isoscalar neutron-proton pairing, for which the experimental “smoking gun" remains elusive. In the present work, proton emission from the lanthanum isotope La59, 23 neutrons away from the only stable isotope La82, is reported. 116La nuclei were synthesised in the fusion-evaporation reaction 58Ni(64Zn, p5n)116La and identified via their proton radioactivity using the mass spectrometer MARA (Mass Analysing Recoil Apparatus) and the silicon …

States in the N= 35 and 37 isotopes 55, 57 Ca have been populated by direct proton-induced nucleon removal reactions from 56, 58 Sc and 56 Ca beams at the RIBF. In addition, the (p, 2 p) quasi-free single-proton removal reaction from 56 Ca was studied. Excited states in 55 K, 55 Ca, and 57 Ca were established for the first time via in-beam γ-ray spectroscopy. Results for the proton and neutron removal reactions from 56 Ca to states in 55 K and 55 Ca for the level energies, excited state lifetimes, and exclusive cross sections agree well with state-of-the-art theoretical calculations using different approaches. The observation of a short-lived state in 57 Ca suggests a transition in the calcium isotopic chain from single-particle dominated states at N= 35 to collective excitations at N= 37.

Excited states in the neutron-deficient nucleus Tc 87 have been studied via the fusion-evaporation reaction Fe 54 (Ar 36, 2 n 1 p) Tc 87 at 115 MeV beam energy. The AGATA γ-ray spectrometer coupled to the DIAMANT, NEDA, and Neutron Wall detector arrays for light-particle detection was used to measure the prompt coincidence of γ rays and light particles. Six transitions from the deexcitation of excited states belonging to a new band in Tc 87 were identified by comparing γ-ray intensities in the spectra gated under different reaction channel selection conditions. The constructed level structure was compared with the shell model and total Routhian surface calculations. The results indicate that the new band structure in Tc 87 is built on a spherical configuration, which is different from that assigned to the previously identified oblate yrast rotational band.

In the past 30 years, synthesis of new isotopes and study of their decay properties have been remaining as high-priority research program at the Institute of Modern Physics, Chinese Academy of Sciences (IMP/CAS). Up to now, 34 new isotopes have been synthesized, 22 of which are heavy and super-heavy nuclei. In this paper, the techniques used and the results obtained at IMP/CAS for the study of heavy and super-heavy nuclei and elements are reviewed chronologically and the perspectives in the near future are introduced.

We investigate the effect of ellipticity ratio of the polarized radiation field on optoelectronic properties of a two-dimensional (2D) semi-Dirac (SD) system. The optical conductivity is calculated within the energy balance equation approach derived from the semiclassical Boltzmann equation. We find that there exists the anisotropic optical absorption induced via both the intra-and interband electronic transition channels in the perpendicular x x and y y directions. Furthermore, we examine the effects of the ellipticity ratio, the temperature, the carrier density, and the band-gap parameter on the optical conductivity of the 2D SD system placed in transverse and vertical directions, respectively. It is shown that the ellipticity ratio, temperature, carrier density, and band-gap parameter can play the important roles in tuning the strength, peak position, and shape of the optical conductivity spectrum. The results obtained from this …

Direct lifetime measurements via γ− γ coincidences using a fast timing detector array consisting of LaBr 3 (Ce) scintillators has been applied to determine the lifetime of low-lying states in the semimagic (N= 50) nucleus Ru 94. The experiment was carried out as the first in a series of “FAIR-0” experiments with the DESPEC experimental setup at the Facility for Antiproton and Ion Research (FAIR). Excited states in Ru 94 were populated primarily via the β-delayed proton emission of Pd 95 nuclei, produced in the projectile fragmentation of an 850 MeV/nucleon Xe 124 beam impinging on a 4 g/cm 2 Be 9 target. While the deduced E 2 strength for the 2+→ 0+ transition in the yrast cascade follows the expected behavior for conserved seniority symmetry, the intermediate 4+→ 2+ transition exhibits a drastic enhancement of transition strength in comparison with pure-seniority model predictions as well as standard shell …

The discovery of the new proton emitter La , 23 neutrons away from the only stable La isotope, La , is reported. The La nuclei were synthesised in the fusion-evaporation reaction Ni ( Zn, p4n) La and identified via their proton radioactivity using the MARA mass spectrometer and the silicon detectors placed at its focal plane. Comparisons of the measured proton energy ( keV) and half-life ( ms) with values calculated using% microscopic nuclear barrier penetration theory the Universal Decay Law approach indicate that the proton is emitted with an orbital angular momentum and that its emission probability is enhanced relative to its closest, less exotic, odd-even lanthanum isotope ( La ) while the proton-emission -value is lower. We propose this to be a signature for the presence of strong neutron-proton pair correlations in this exotic, neutron deficient system. The observations of decays from isomeric states in La and La are also reported.

The one-neutron knockout from Ca 52 in inverse kinematics onto a proton target was performed at∼ 230 MeV/nucleon combined with prompt γ spectroscopy. Exclusive quasifree scattering cross sections to bound states in Ca 51 and the momentum distributions corresponding to the removal of 1 f 7/2 and 2 p 3/2 neutrons were measured. The cross sections, interpreted within the distorted-wave impulse approximation reaction framework, are consistent with a shell closure at the neutron number N= 32, found as strong as at N= 28 and N= 34 in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 1 f 7/2 and 2 p 3/2 orbitals of 0.61 (23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the 2 p 3/2 orbital in neutron-rich Ca isotopes is responsible for the …

Two rotational bands are identified in Cs, one of which having very similar pattern to that of the strongly-coupled band. The properties of the bands with similar patterns extracted from the experimental data are in agreement with a chiral interpretation. Tilted axis cranking covariant density functional theory with pairing correlations and particle-number conserving cranked shell model calculations are employed to determine the deformation and to investigate the band configurations, respectively. It results that the backbending is induced by the rotational alignment of two protons, whose angular momenta reorient from the short to the intermediate axis, in a plane orthogonal to the angular momentum of the strongly-coupled proton which keeps aligned along the long axis. The total spin points in 3D, inducing the breaking of the chiral symmetry. This is the first observation of candidate chiral bands built on …

The DEcay SPECtroscopy (DESPEC) setup for nuclear structure investigations was developed and commissioned at GSI, Germany in preparation for a full campaign of experiments at the FRS and Super-FRS. In this paper, we report on the first employment of the setup in the hybrid configuration with the AIDA implanter coupled to the FATIMA LaBr(Ce) fast-timing array, and high-purity germanium detectors. Initial results are shown from the first experiments carried out with the setup. An overview of the setup and function is discussed, including technical advancements along the path.