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Deep-inelastic collisions of a 208Pb beam on a 208Pb target were performed using the ATLAS accelerator at Argonne National Laboratory. Prompt and delayed -rays from the reaction products were detected using the GAMMASPHERE detector array. The cross-coincidence method was used to identify transitions in 207Tl, by gating on -rays from its bettercharacterised reaction partner 209Bi. A number of new transitions were found in 207Tl. [ABSTRACT FROM AUTHOR]

The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During ?+-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy for the decay of 100Sn, the heaviest doubly magic nucleus with equal numbers of protons and neutrons. In the ?-decay of 100Sn, a large fraction of the strength is observable because of the large decay energy. We determine the largest Gamow-Teller strength so far measured in allowed nuclear ?-decay, establishing the 'superallowed' nature of this Gamow-Teller transition. The large strength and the low-energy states in the daughter nucleus, 100In, are well reproduced by modern, large-scale shell model calculations. [ABSTRACT FROM AUTHOR]

The energy centroids and integrated strengths of Gamow-Teller transitions in the $ \beta^{+}_{}$ and electron-capture decay are analyzed for nuclei whose proton number Z and neutron number N are restricted to 44 $ \leq$ Z $ \leq$ 50 and 50 $ \leq$ N $ \leq$ 58 . The analysis is based on data measured both with high-resolution $ \gamma$ -ray spectrometry and total $ \gamma$ -ray absorption techniques. The dependence of the considered quantities on the relative neutron excess are established after taking into account the effects due to the Coulomb interaction and mean-field level occupancies. An extrapolation of this dependence to the lightest known tin isotopes is used to estimate the decay characteristics of Sn and Sn . The values extrapolated for the half-lives of Sn and Sn agree with experimental data. Using the extrapolated values together with shell model predictions, the Q values for the electron-capture decay of Sn is evaluated. The quenching factor for $ \beta^{+}_{}$ and the electron-capture decay of the nuclei under consideration here is established to be 0.56(2) with a possible weak dependence on N - Z . [ABSTRACT FROM AUTHOR]

Heavy neutron-rich nuclei have been populated through the relativistic fragmentation of a $\ensuremath ^{208}_{\ 82}{\rm Pb}$ beam at $\ensuremath E/A = 1$ GeV on a $\ensuremath 2.5 {\rm g/cm^2}$ thick Be target. The synthesised nuclei were selected and identified in-flight using the fragment separator at GSI. Approximately 300 ns after production, the selected nuclei were implanted in an $\ensuremath \sim 8$ mm thick perspex stopper, positioned at the centre of the RISING $\ensuremath \gamma$ -ray detector spectrometer array. A previously unreported isomer with a half-life $\ensuremath T_{1/2} = 163(5)$ ns has been observed in the N = 126 closed-shell nucleus $\ensuremath ^{205}_{\ 79}{\rm Au}$ . Through $ \gamma$ -ray singles and $ \gamma$ - $ \gamma$ coincidence analysis a level scheme was established. The comparison with a shell model calculation tentatively identifies the spin-parity of the excited states, including the isomer itself, which is found to be $\ensuremath I^{\pi} = (19/2^+)$ . [ABSTRACT FROM AUTHOR]

Heavy neutron-rich nuclei were populated via relativistic energy fragmentation of a E/A = 1 GeV208Pb beam. The nuclei of interest were selected and identified by a fragment separator and then implanted in a passive plastic stopper. Delayed γ rays following internal isomeric decays were detected by the RISING array. Experimental information was obtained on a number of nuclei with Z = 73-80 (Ta-Hg), providing new information both on the prolate-oblate transitional region as well as on the N = 126 closed shell nuclei. [ABSTRACT FROM AUTHOR]

The nuclear structure of neutron-rich N > 126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A = 1 GeV 238U beam on a Be target. The preliminary analysis indicates the presence of previously unreported isomeric states in the N = 128 isotones 208Hg and 209Tl. [ABSTRACT FROM AUTHOR]

Preliminary results from the first experiment of the Stopped Beam RISING campaign are presented. The relativistic projectile fragmentation of a 750 MeV/u beam of 107Ag populated isomeric states in very neutron deficient nuclei at the proton dripline around mass 80-90. Nuclei were unambiguously identified using the FRagment Separator (FRS) and its ancillary detectors located at GSI. The ions produced were slowed down from relativistic energies by means of an Al degrader and implanted in the centre of the high-efficiency Stopped RISING array. This allowed the identification of new excited states in the N = Z = 43 nucleus, 86Tc, populated following the de-excitation of a microsecond isomer. Preliminary results of this analysis, as well as previously unobserved isomeric states in 87,88Tc, are reported. [ABSTRACT FROM AUTHOR]

The β decay of 94Ag, a nucleus with three proton and three neutron holes with respect to 100Sn, was investigated at the GSI on-line mass separator by using an array of germanium and silicon detectors. On the basis of a βγγ coincidence measurement, the previously reported decay scheme has been considerably improved and evidence is presented for a spin–gap isomer with a spin-parity assignment of (21+), i.e., the highest spin ever observed in β decay. The half-life of the low-spin isomer (7+) was remeasured to be 0.59(2) s, whereas the half-life of the high-spin isomer was determined as 0.47(8) s. For the states in 94Ag and 94Pd, large-scale shell-model calculations that include up to 4p–4h excitations across the N=Z=50 shell gap and employ a realistic interaction were carried out. These core excitations play a crucial role in generating the E4 isomerism required for the interpretation of the long half-life of the (21+) state in 94Ag. [Copyright &y& Elsevier]

In a high-energy fragmentation experiment at GSI an I = π (6 +) isomer and its γ -decay are identified in 102Sn, the two-neutron neighbour of the doubly-magic 100Sn. Its half-life is measured to be T = 1 / 2 367 (11) ns. The possible existence of further isomers is discussed in the framework of large-scale shell model (LSSM) calculations including up to five particle-hole excitations of the 100Sn core. From the precise B(E2; 6 + → 4 +) strength and the recently remeasured value for B(E2; 8 + → 6 +) in the two-proton hole neighbour 98Cd effective E2 polarization charges for protons and neutrons were inferred including LSSM corrections within the full N=4 0 ħ ω space. The results are discussed in comparison to predicted and empirically determined effective operators. [ABSTRACT FROM AUTHOR]

The β decay of the semi-magic nucleus 130Cd has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of 130In and the observation of additional β feeding to high-lying core-excited states in 130In. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N=50-82 neutron and Z=28-50 proton shells and the NA-14 interaction, and good agreement is found. [ABSTRACT FROM AUTHOR]

We report the results from the first experiment to measure gyromagnetic factors of μs isomers in neutron-rich nuclei produced by intermediate-energy projectile-fragmentation reactions. The Time Dependent Perturbed Angular Distribution (TDPAD) method was applied in combination with the heavy-ion-gamma correlation technique. The nuclides in the vicinity of 68Ni were produced and spin-oriented following the fragmentation of a 76Ge, 61.4 MeV/u beam at GANIL. The results obtained, |g|(69mCu) = 0.225(25) and |g|(67mNi) = 0.125(6) provide another indication of the importance of proton excitation across the Z = 28 shell gap for the description of these states. [ABSTRACT FROM AUTHOR]

The single closed-neutron-shell, one proton–hole nucleus 207 Tl was populated in deep-inelastic collisions of a 208 Pb beam with a 208 Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupole phonon state and a large number of core excited states. Based on shell-model calculations, all observed single core excitations were established to arise from the breaking of the N = 126 neutron core. While the shell-model calculations correctly predict the ordering of these states, their energies are compressed at high spins. It is concluded that this compression is an intrinsic feature of shell-model calculations using two-body matrix elements developed for the description of two-body states, and that multiple core excitations need to be considered in order to accurately calculate the energy spacings of the predominantly three-quasiparticle states. [ABSTRACT FROM AUTHOR]

The four-proton hole 96Pd neighbor of the doubly-magic 100Sn nucleus was studied in-beam, using a fusion-evaporation reaction of a 58Ni beam on a 45Sc target. States of 96Pd were established up to an excitation energy of 9707 keV. A core-excited odd-parity isomer with T½ = 37.7(1.1) ns was identified. Shell model calculations were performed in four different model spaces. Even-parity states of 96Pd are very well reproduced in large-scale shell model (LSSM) calculations in which excitations are allowed of up to five g9/2 protons and neutrons across the N = Z = 50 gap, to the g7/2, d5/2, d3/2, and S½ orbitals. The odd-parity isomer can be only qualitatively interpreted though, employing calculation in the full f p g shell model space, with just one particle-hole core excitation. [ABSTRACT FROM AUTHOR]

Abstract: The first excited states in 54,56,58Cr were populated by Coulomb excitation at relativistic energies and γ rays were measured using the RISING setup at GSI. For 56Cr and 58Cr the values relative to the previously known value for 54Cr are determined as 8.7(3.0) and 14.8(4.2) W.u., respectively. The results are consistent with a subshell closure at neutron number which was already indicated by the higher energy of the state in 56Cr. Recent large-scale shell model calculations using effective interactions reproduce the trend in the excitation energies, but fail to account for the minimum in the values at . [Copyright &y& Elsevier]

Reduced transition strengths of the deexciting transitions from the first two excited states in 33Ar were measured in a relativistic Coulomb excitation experiment at the GSI Helmholtz center. The radioactive ion beam was produced by fragmentation of a primary 36Ar beam on a 9Be target followed by the selection of the reaction product of interest via the GSI Fragment Separator. The 33Ar beam hit a secondary 197Au target with an energy of approximately 145 MeV/nucleon. An array of high-purity germanium cluster detectors and large-volume BaF2 scintillator detectors were employed for γ-ray spectroscopy at the secondary target position. The Lund-York-Cologne Calorimeter was used to track the outgoing ions and to identify the nuclear reaction channels. For the two lowest energy excited states of 33Ar the reduced transition strengths have been determined. With these first results the Tz = -3/2 nucleus 33Ar is now, together with 21Na (Tz = -1/2), the only neutron-deficient odd-A sd shell nucleus in which experimental transition strengths are available. The experimental values are compared to results of shell-model calculations which describe simultaneously mirror-energy differences and transition-strength values of mirror pairs in the sd shell in a consistent way. [ABSTRACT FROM AUTHOR]

The ß decay of five heavy, neutron-rich nuclei, 203,204Pt and 200-202Ir, has been investigated following relativistic cold fragmentation reactions of lead projectiles using the FRS+RISING setup at GSI. This paper reports on the study of the low-lying states in the decay daughter nuclei 203,204Au and 200-202Pt. The characteristic γ rays for each nucleus have been determined using ß-delayed γ-ray spectroscopy. Tentative level schemes, relative intensities, and apparent ß feedings are provided. These data are compared with shell-model calculations, which indicate a substantial contribution to the total ß strength from high-energy first-forbidden ß-decay transitions in this mass region. [ABSTRACT FROM AUTHOR]

This Brief Report reports on the first observation of the β--delayed γ decay of 215Pb, feeding states in 215Bi. The 215Pb beam was produced using resonant laser ionization and mass separated at the ISOLDE-CERN on-line mass separator. This ensured clean identification of the γ rays as belonging to the decay of 215Pb or its γ-decay daughters. A half-life of 147(12) s was measured for the 215Pb β decay and a level scheme for the daughter nucleus 215Bi is proposed, resulting in an extended systematics of the excited states of the neutron-rich Bi isotopes. [ABSTRACT FROM AUTHOR]

A ß-decaying high-spin isomer in 96Cd, with a half-life T1/2 = 0.29 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. S, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of 124Xe on a 9Be target. From the half-life and the observed γ decays in the daughter nucleus, 96Ag, we conclude that the ß-decaying state is the long predicted 16+ "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πv(P1/2, g9/2) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N = Z = 50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the π v(g, d, s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer. [ABSTRACT FROM AUTHOR]

A decay spectroscopic study of the neutron-rich isotopes has been performed using fragmentation of a 86Kr primary beam. Fragments from this reaction have been selected by the LISE2000 spectrometer at the Grand Accélérateur National d'Ions Lourds (GANIL). Half-lives of 29 isotopes, including the first ones identified for 61Ti (15±4 ms), 64V (19±8 ms), and 71Fe (28±5 ms), have been determined and compared with model predictions. 67,68Mn β-delayed γ rays were observed for the first time. The branching for the β-delayed neutron emission was measured to be greater than 10(5)% in the 67Mn decay. The 67Fe isomeric level is firmly determined at higher energy than assigned in previous works. The excitation energies of the first (2+) and (4+) states of 68Fe are suggested to lie at 522(1) and 1389(1) keV, respectively, thus bringing confirmation of assignments based on in-beam γ-ray spectroscopy. Beyond-mean-field calculations with the Gogny D1S force have been performed for even-mass nuclei through the Fe isotopic chain. Not only 68Fe but most of the neutron-rich Fe isotopes with neutron numbers below N=50 are interpreted as soft rotors. The calculated mean occupancy of the neutron g9/2 and d5/2 orbitals in correlated ground states is steadily growing with increasing neutron number throughout the isotopic chain. Interpretation of 67Fe data is based upon the present calculations for the 66Fe and 68Fe even cores. [ABSTRACT FROM AUTHOR]

Abstract: We report on the g factor measurement of the isomeric state (, ) in the neutron-rich 126Sn nucleus. The nucleus was produced by the fission of a relativistic 238U beam and reaction products were selected by the FRS fragment separator at GSI. For the first time, spin-alignment was observed after relativistic fission. It was used to deduce the g factor of the isomeric state, , from the measured perturbed angular distribution of its γ decay using the RISING Cluster detectors. The observed value confirms the suggested dominant configuration, which has been proposed for the isomers in neutron-rich Sn isotopes. The failure of the g factor additivity rule and the importance of core polarization evolution with increasing distance from the doubly-magic 132Sn is discussed. The first observation of 18(8)% of spin-alignment produced by the relativistic fission of a 238U beam paves the way to study moments of neutron-rich (sub-)microsecond isomers, which are difficult to align by other means. [Copyright &y& Elsevier]

Heavy neutron-rich nuclei have been populated through the relativistic fragmentation of a $\ensuremath ^{208}_{\ 82}{\rm Pb}$ beam at $\ensuremath E/A = 1$ GeV on a $\ensuremath 2.5 {\rm g/cm^2}$ thick Be target. The synthesised nuclei were selected and identified in-flight using the fragment separator at GSI. Approximately 300 ns after production, the selected nuclei were implanted in an $\ensuremath \sim 8$ mm thick perspex stopper, positioned at the centre of the RISING $\ensuremath \gamma$ -ray detector spectrometer array. A previously unreported isomer with a half-life $\ensuremath T_{1/2} = 163(5)$ ns has been observed in the N = 126 closed-shell nucleus $\ensuremath ^{205}_{\ 79}{\rm Au}$ . Through $ \gamma$ -ray singles and $ \gamma$ - $ \gamma$ coincidence analysis a level scheme was established. The comparison with a shell model calculation tentatively identifies the spin-parity of the excited states, including the isomer itself, which is found to be $\ensuremath I^{\pi} = (19/2^+)$ . [ABSTRACT FROM AUTHOR]

Excited states of the neutron deficient 101Ag nucleus have been investigated via the 50Cr(58Ni, 3p1α) heavy-ion induced reaction at 261 MeV by use of in-beam spectroscopic methods. On the basis of the measured γγ-coincidence relations and angular distribution ratios high-spin bands have been extended up to Iπ=35/2+, 45/2(−) and (49/2−). The negative parity states at the highest energy have been interpreted as terminating non-collective oblate states in the framework of the Nilsson–Strutinsky cranking formalism. [Copyright &y& Elsevier]

Background: The even cadmium isotopes near the neutron midshell have long been considered among the best examples of vibrational nuclei. However, the vibrational nature of these nuclei has been questioned based on E2 transition rates that are not consistent with vibrational excitations. In the neighboring odd-mass nuclei, the g factors of the low-excitation collective states have been shown to be more consistent with a deformed rotational core than a vibrational core. Moving beyond the comparison of vibrational versus rotational models, recent advances in computational power have made shell-model calculations feasible for Cd isotopes. These calculations may give insights into the emergence and nature of collectivity in the Cd isotopes. Purpose: To investigate the nature of collective excitations in the A ≈ 100 region through experimental and theoretical studies of magnetic moments and electromagnetic transitions in 111Cd. Method: The spectroscopy of 111Cd has been studied following Coulomb excitation. Angular correlation measurements, transient-field g-factor measurements and lifetime measurements by the Doppler-broadened line shape method were performed. The structure of the nucleus was explored in relation to particle-vibration versus particle-rotor interpretations. Large-scale shell-model calculations were performed with the SR88MHJM Hamiltonian. Results: Excited-state g factors have been measured, spin assignments examined, and lifetimes determined. Attention was given to the reported 5/2+ 753-keV and 3/2+ 755-keV states. The 3/2+ 755-keV level was not observed; evidence is presented that the reported 3/2+ state was a misidentification of the 5/2+ 753-keV state. Conclusions: It is shown that the g factors and level structure of 111Cd are not readily explained by the particle-vibration model. A particle-rotor approach has both successes and limitations. The shell-model approach successfully reproduces much of the known low-excitation structure in 111Cd. [ABSTRACT FROM AUTHOR]