Search

We report on the g factor measurement of the isomeric 7 − state ( E * = 2219 keV , T 1 / 2 = 5.9 ( 8 ) μs ) 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 7 − isomeric state, g ( 7 − ) = − 0.098 ( 9 ) , from the measured perturbed angular distribution of its γ decay using the RISING Cluster detectors. The observed value confirms the suggested ν ( h 11 / 2 − 1 d 3 / 2 − 1 ) dominant configuration, which has been proposed for the 7 − 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.

The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV $\ensuremath I^{\pi}=12^+$ isomer in 192Pb with $ \tau$ = 1.57 μs has been produced using the fragmentation of a 1A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, $ \tau$ = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.

Lifetimes of low-lying states in 123,123Cs and 120,122XE are measured using the recoil-distance Doppler-shift method. The investigated nuclei were produced by the 107Ag+18O and 109Ag+18O reactions. The negative-parity states in 121,123Cs are described in the framework of the core-quasiparticle coupling model with gamma -soft (the extended Wilets-Jean model) and rigid (the Davydov-Filippov model) cores. The comparison of experimental and theoretical reduced E2 transition probabilities between the yrast negative-parity states in 121,123Cs seems to indicate that the corresponding cores cannot be fully gamma -soft as in the completely gamma -unstable model of Wilets and Jean (1956). This does not necessarily mean that the cores are as rigid as the Davydov-Filippov model assumes, but rather indicates a localization of the nucleus in the prolate ( gamma

The reaction58Ni(36Ar,α qρ)88Mo has been studied at 145 MeV beam energy. A detector array consisting of the OSIRIS spectrometer, four charged-particleΔE detectors and seven NE213 neutron detectors has been used to meaure the gamma radiation inγγ- and particle-γγ-coincidence mode. The level scheme of88Mo has been extended up to 11.6 MeV excitation energy and probable spin 23ħ; some 70 transitions and 40 levels have been identified. Spin assignments have been proposed on the basis of measured DCO ratios. Hartree Fock cranking calculations of the Total Routhians and shell model calculations of the high spin states are presented which imply near-sphericity of the yrast line up to the highest spins found. A classification of the high spin states according to their leading seniority is proposed.

High-spin states in 152Er have been populated through the Sn-116(Ar-40,4n)152Er reaction. Prompt and delayed gamma-gamma-gamma-t and gamma-e-t coincidences have been measured. Levels and transitions are assigned up to an excitation energy of 15 MeV and spin and parities up to 28+ at 9.7 MeV. A new isomer [t1/2 = 11(1) ns] has been observed at 13.4 MeV. The results are discussed in comparison with neighboring nuclei and with shell-model calculations.

The reaction58Ni(36Ar, 4p)90Mo has been studied at a beam energy of 149 MeV. A detector array consisting of the OSIRIS spectrometer (12 Compton-suppressed Ge detectors), four charged-particleδE detectors and seven NE-213 neutron detectors at the VICKSI accelerator in Berlin has been used to measure the gamma radiation inγγ- and particle-γγ-coincidence mode. An additional Ge detector was placed at 162‡ to the beam direction to provide information on DCO ratios. The level scheme of90Mo has been extended up to an excitation energy of about 12 MeV and probable spin 23ħ. Some 70 transitions and 40 levels have been newly identified. Spin assignments have been proposed on the basis of measured DCO ratios. Shell model calculations in a model space consisting of the proton 1f 5/2, 2p 3/2, 2p 1/2, and 1g 9/2 orbits and the neutron 2p 1/2, 1g 9/2, 1g 7/2, 2d 5/2, 2d 3/2, and 3s 1/2 orbits with some truncation were made for states above 9ħ and the predicted structure of these states is discussed.

For the first time, detailed decay-spectroscopic investigations were performed for the very neutron-deficientN=50 nuclide98Cd. The98Cd activity was produced in spallation reactions between 600 MeV protons and a natural tin target, yielding a98Cd beam intensity of 10 to 60 atoms/s at the collector of the ISOLDE massseparator. By means ofγ-ray and conversion-electron spectroscopy, 19 transitions were found to follow the β+/EC decay98Cd→98Ag. The transitions at 61 and 107 keV were shown to beM1(+E2) andE2, respectively, and the98Cd half-life was measured as 9.2±0.3 s. TheQ EC value of98Cd is determined semiempirically and is compared to model predictions together with the measuredQ EC values of the neighbouring cadmium isotopes100,102Cd and theN=50 isotones92Mo,94Ru, and96Pd, taken from the literature. The newly established decay scheme of98Cd includes 9 excited states of98Ag. Four states at 1691, 1861, 2164, and 2544 keV are directly fed by 0+ → 1+ Gamow-Teller beta transitions with a summed strength of 3.5 −0.7 +0.8 . This value corresponds to 25±5% of the strength predicted for the GT transformation of a g9/2 proton (in98Cd) into a g7/2 neutron (in98Ag) by the extreme single-particle shell model. The GT-strength splitting and quenching, observed for98Cd, are compared with the corresponding data for lighter even-even N=50 isotones, and are discussed with reference to the predictions of more sophisticated nuclear models. We find that only in some cases it is possible to explain qualitatively the observed GT strength distribution and its total magnitude without renormalizing the free-neutron value of the axial-vector coupling constant.

The neutron-deficient nuclei100,101Cd were identified for the first time in — beam following the reactions58Ni +46,48Ti and58Ni +50Cr at 230 MeV and 245 MeV bombarding energy of the58Ni beams. Theγ-decay of the isotopes100,101,102Cd was studied inpγ, ppγ,nγ, nnγ, andnγγ prompt and delayed coincidence spectra. Isomers were found with spin and half life {ie1-01}=8+, T1/2=52(5) ns in100Cd, {ie1-02}=(19/2+), T1/2=4.6(4) ns in101Cd and {ie1-03}=8+, T1/2=56(4) ns in102Cd. In a PAD experiment theg-factor of the {ie1-04}=8+ isomer in100Cd was measured to be g=1.24(6). Using the reaction36Ar +70Ge at 135 MeV energy of the36Ar beam, theg-factor and the quadrupole moment of the {ie1-05}=8+ isomer in102Cd were measured to be g=1.29(3) and Q=87(10) fm2, respectively. The spectroscopic results are discussed within a shell model approach using a100Sn core, which accounts well for the electromagnetic properties of the proton aligned isomers. The structure of the spherical neutron states, dominated by the close lying vd5/2, g7/2 orbitals, and the gradually developing quadrupole collectivity are reproduced by the shell model calculations.

The conditions for production of radioactive ion-beams from targets of refractory metals by addition of CF4 gas have been investigated. The production yields of chemically pure mass separated beams, obtained through the formation of molecular ions, are described for the elements Ca, Sc, Sr, Y, (Zr), Ba, Lu, and Hf. Improved release properties are obtained for several elements, owing to the formation of volatile chemical compounds in the target. Production yield curves are presented, and applications to other targets and elements are briefly discussed.

The experimental techniques and recent results of nuclear structure studies in-beam close to 100Sn are reviewed. The structure of the nuclides 97Ag, 100Cd and 104Sn, so far the nuclei of closest approach to 100Sn with known excited states, is discussed within the spherical shell model. The basic shell model parameters of 100Sn, single particle binding energies and two-body matrix elements, as deduced from the shell model analysis, are summarized. From the available structure information conclusions are drawn for the design and expected phenomena of future experiments towards the far-from-stability doubly magic 100Sn.

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 U-238 beam. Metastable states in the N=128 isotones Hg-208 and Tl-209 have been identified. Delayed gamma-ray transitions are interpreted as arising from the decay of I-pi=(8(+)) and (17/2(+)) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z 126.

The relativistic projectile fragmentation of a 750 MeV per nucleon beam of Ag-107 was used to populate isomeric states in neutron-deficient nuclei around A=80-90. Reaction products were separated and unambiguously identified using the GSI FRagment Separator (FRS) and its ancillary detectors. At the final focal plane, the fragments were slowed from relativistic energies by means of an aluminium degrader and implanted in a passive stopper in the center of the high-efficiency, high-granularity Stopped Rare Isotope Spectroscopic INvestigation at GSI (RISING) germanium array. This allowed the identification of excited states in the N=Z nuclei Tc-86(43) and, for the first time, Nb-82(41). Isomeric states have also been identified for the first time in Tc-87,Tc-88, and a previously unreported isomer was observed in Nb-84. Experimental results are presented along with a discussion on the structure of these nuclei based on interpretations provided by several theoretical models. (Less)

Heavy neutron-rich nuclei have been populated through the relativistic fragmentation of a Pb-208(82) beam at E/A = 1 GeV on a 2.5 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 similar to 8 mm thick perspex stopper, positioned at the centre of the RISING gamma-ray detector spectrometer array. A previously unreported isomer with a half-life T-1/2 = 163(5) ns has been observed in the N = 126 closed-shell nucleus Au-205(79). 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 I-pi = (19/2(+)).

The γ-ray decay of isomeric states in the even-even nucleus Cd128 has been observed. The nucleus of interest was produced both by the fragmentation of Xe136 and the fission of U238 primary beams. The level scheme was unambiguously constructed based on γγ coincidence relations in conjunction with detailed lifetime analysis employed for the first time on this nucleus. Large-scale shell-model calculations, without consideration of excitations across the N=82 shell closure, were performed and provide a consistent description of the experimental level scheme. The structure of the isomeric states and their decays exhibit coexistence of proton, neutron, and strongly mixed configurations due to πν interaction in overlapping orbitals for both proton and neutron holes. © 2009 The American Physical Society., Supported by the Spanish Ministerio de Educación y Ciencia under Contracts FPA2005-00696 and FPA2007-66069, the European Commission Contract 506065 (EURONS), the Swedish VR, EPSRC, and STFC (United Kingdom), the German BMBF, the Polish Ministry of Science and Higher Education (Grants 1-P03B-030-30 and 620/E-77/SPB/GSI/P 03/DWM105/2004-2007), and the Bulgarian Science Fund.

Heavy neutron-rich nuclei were populated via relativistic energy fragmentation of a E / A = 1 GeV 208 Pb 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.

4 pags., 3 figs. -- PACS:21.10.-k21.10.Pc21.10.Tg21.60.Cs23.20.Lv, The γ-ray decay of an excited state in 131In, the one proton hole neighbor of the doubly magic 132Sn has been measured. A high-spin, core-excited isomer with T1 / 2 = 630 (60) ns was identified following production by both relativistic fragmentation of a 136Xe beam and fission of a 238U beam. This state deexcites by a single γ-ray branch of 3782(2) keV from which direct evidence for the size of the N = 82 shell gap is inferred. The results are discussed in comparison to a shell-model calculation including configurations across the closed shells at N = 82 and Z = 50. © 2009 Elsevier B.V. All rights reserved., This work is supported by the EU Access to LargeScale Facilities Programme (EURONS, EU contract 506065), the Polish Ministry of Science and Higher Education (1-P03B-030-30 and620/E-77/SPB/GSI/P-03/DWM105/2004-2007), the Spanish Ministerio de Educacion y Ciencia (FPA2005-00696, FPA2005-00732 andFPA2007-66069), EPSRC/STFC (UK), The Swedish Research Council,The Bulgarian Science Fund VUF06/05, The US Dept. of Energy (DE-FG02-91ER-40609 and DE-AC02-06CH11357), The German Federal Ministry of Education and Research (06KY205I), The Hungarian Sci-ence Foundation (OTKA K-68801) and the Italian INFN

The gamma-decay of excited states in the neutron deficient isotopes Tc-87 and Tc-88 has been observed for the first time. The fusion-evaporation reactions Ni-58(S-32, p2n)Tc-87 and Ni-58(S-32, pn)Tc-88 at 110 MeV, Ca-40(Cr-50, p2n)Tc-87 and Ca-40(Cr-50, pn)Tc-88 at 170 MeV and Ni-58(Ar-36, alpha-pn)Tc-88 at 145 MeV beam energy were used. Unambiguous identification of these nuclei which are populated with less than 1 mb cross section was achieved with coincidences between the gamma-radiation and the evaporation residues detected in a recoil mass separator. From gamma-gamma-coincidence data, a decay scheme of 11 transitions was constructed for Tc-88, the ground state of which is suggested to have I-pi = 7- or 8+. Two transitions identified in Tc-87 follow the pattern of a g9/2 one-quasiparticle band. (Less)

The level structure of196Po has been studied using a160Dy(40Ar, 4n) reaction and a recoil-catcher technique to reduce fission. The results showed a sharp drop off in the first (2+) and (4+) energies relative to systematics implying an abrupt increase in the quadrupole collectivity at N=112. In addition, second (2+) and(4+) states were identified at 859 and 1388 keV, respectively, suggesting the discovery of a 4p2h deformed band in Po isotopes which is related to known 2p2h proton bands in several Pb isotopes. A prompt183W(20Ne, 5n@#@) experiment located similar second 2+ and 4+ states at 1039 and 1483 keV in198Po providing corroboration and extended information on the properties of the new Po deformed bands. A measured halflife of 850 (90) ns for the 2491 keV (11−) state in196Po implied collective E3 contributions to the extractedB (@#@ E3; 11−→8+)=27(5) W.u.

High-spin states in 146 Nd and 148 Sm have been populated using the 3 C+ 136 Xe and 22 Ne+ 130 Te compund nucleus reactions. Alternating parity bands built on the ground state are observed to spin I = (19) and I = (27) in 146 Nd and 148 Sm respectively. Analysis of the data done in terms of the reflection-asymmetric mean-field approach suggests that both nuclei become octupole-unstable at medium spins. The observed enhancement of E1 rates supports this prediction. In 148 Sm also a structure with simplex quantum number s = −1 is observed. At medium spins the reflection-asymmetric structures coexist with reflection-symmetric configurations. The decrease of the electric dipole moment observed for the N = 86 isotones between Z = 62 and Z = 64 is explained by the transition from static to dynamical octupole correlations.

The four proton-hole nucleus Pt-204 was populated in the fragmentation of an E/A = 1 GeV Pb-208 beam. The yrast structure of Pt-204 has been observed up to angular momentum I = 10h by detecting delayed gamma-ray transitions originating from metastable states. These long-lived excited states have been identified to have spin-parities of I-pi = (10(+)), (7(-)), and (5(-)) and half-lives of T-1/2 = 146(14) ns, 55(3) mu s, and 5.5(7) mu s, respectively. The structure of the magic N = 126 Pt-204 nucleus is discussed and understood in terms of the spherical shell model. The data suggest a revision of the two-body interaction for N = 126, Z < 82, which determines the evolution of nuclear structure toward the r-process waiting point nuclei.

A recent publication describes results obtained by in-beam $\ensuremath{\gamma}$-ray spectroscopy of excited states of $^{92}\mathrm{Rh}$ and concludes, by mainly using extrapolated $Q$ values, that the previously reported direct two-proton decay of $^{94}\mathrm{Ag}$ (${21}^{+}$) to $^{92}\mathrm{Rh}$ is very difficult to reconcile with the $\ensuremath{\gamma}$-ray data. We present evidence that this conclusion may be misleading.

The 2(1)(+) states of Sn-114,Sn-116 were excited in two consecutive experiments by means of Coulomb excitation in inverse kinematics on a Ni-58 target. A precise determination of the reduced transition probability B(E2; 0(g.s.)(+) -> 2(1)(+)) of Sn-114 relative to the well-known 2(1)(+) excitation strength in Sn-116 was achieved by comparing the relative projectile to target 2(1)(+) -> 0(g.s.)(+) decay intensities. The obtained B(E2 up arrow) value of 0.232(8)e(2)b(2) for Sn-114 confirms the tendency of large B(E2 up arrow) values for the light tin isotopes below the midshell Sn-116 that has been observed recently in various radioactive ion beam experiments. The result establishes most clearly the discrepancy between the current B(E2 up arrow) value predictions from large-scale shell-model calculations and the experimental deviation, which commences already for the stable Sn-114 isotope. (Less)

International audience; The neutron orbitals h(11/2), d(3/2), s(1/2), determine the structure of the abundant yrast traps in the neutron-rich Sn isotopes close to (132)Sn. In (125,127,129)Sn the high-spin members of the nu(d(3/2)(-1)h(11/2)(-2)) and nu(h(11/2)(-n)), seniority nu=3, multiplets form isomeric (23/2(+)) [1,2] and (27/2(-)) [2] states which were recently observed in relativistic fission of (238)U and fragmentation of (136)Xe at the RISING setup at GS1. These rather pure states and the mixed 19/2(+) isomers with a dominant nu(s(1/2)(-1)h(11/2)(-2)) configuration [3] are discussed. First evidence for a new isomer in (128)Sn with nu(d(3/2)(-1)h(11/2)(-3)) configuration analogue to the isotone (130)Te [4] is presented.

New sub-mu s isomers have been observed in the neutron-rich Sn isotopes. Sn-125,Sn-127,Sn-129 nuclei have been produced in a relativistic fission reaction of U-238 on a Be-9 target at 750 A.MeV and by the fragmentation of Xe-136 at 600 A.MeV populating high-spin yrast states. In addition to the already known mu s isomers, three new ones with sub-mu s half-lives have been observed. These yrast isomers are the high-spin members of the nu(d(3/2)(-1)h(11/2)(-2)) and nu h(11/2)(-n), seniority v = 3 multiplets leading to isomeric (23/2(+)) and (27/2(-)) states, respectively. Added to the already known 19/2(+)mu s isomers in this region the current work completes the systematic information of neutron-hole excitations toward the filling of the last h(11/2) orbital at N = 82. The results are discussed in the framework of state-of-the-art shell-model calculations using realistic interactions.

The proposals of the EUROBALL Design Group for the development of large composite Ge detectors for an improved 4π detector array with a total full energy peak efficiency of p ph > 0.15 are presented. Cluster detectors are composed of hexagonal tapered coaxial Ge detectors while Stack detectors are composed of large diameter planar detectors. The status of the development is discussed and first experimental results of the properties of a hexagonal tapered Ge detector are presented.

A superdeformed band has been identified in 194 Pb, populated in the 158 Gd( 40 Ar, 4n) reaction. The dynamic moment of inertia J (2) is very similar to the ones of the superdeformed bands in 192 Hg and 194 Hg. This suggests that the high- N intruder configuration π 6 4 ν 7 4 determines the properties of the superdeformed core also in 194 Pb.

Excited states in97Ag have been identified for the first time following the reactions46Ti(58Ni,α p 2n and64Zn(36Ar,p 2n. The population cross sections were 1.0(5) mb and 0.7(3) mb, respectively. Theγ-decay of the seniorityΝ=3 states below theI π=(17/2−) and (21/2+) isomers was investigated. In a search for short lived isomers half lives oft 1/2=5(2) ns and 2.5(5) ns were found in theN=50 isotones97Ag,I π=(17/2−) and/or (21/2+) and95Rh,I π=(21/2+). A new isomer was identified in97Pd,I π=17/2+ witht 1/2=2.3(5) ns. The implication of the three-proton hole spectrum in100Sn for the empirical residual interaction and shell model predictions is discussed.

PAC measurements of the electric field gradient at the nucleus of isolated probe atoms on Pd(111) surfaces lead to the identification of five adsorption sites successively occupied by the parents111In and111mCd during annealing between 80K and 600K. The data are consistent with an estimated activation energy for Pd surface self diffusion of Ea=0.76(8)eV.

198,200 Po nuclei have been studied by in-beam gamma-ray spectroscopy with the 182,184 W( 20 Ne, 4n) reactions. In both nuclei 8 + , 11 − and 12 + isomers have been observed, and their lifetimes and g -factors were measured. The low-spin states show signs of a collective structure, while at higher spins very pure neutron and proton states occur with very little mutual interaction.

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 electromagnetic decay properties of high-spin states in $^{52}\mathrm{Mn}$ have been studied through various experiments with the GASP and EUROBALL arrays plus the ISIS light charged-particle detector and the Neutron Wall. From \ensuremath{\gamma}-\ensuremath{\gamma} particles coincidence measurements, spins, and parities of these states and branching ratios of their decay \ensuremath{\gamma} rays have been determined. Using the Doppler-shift attenuation method the mean life of some states have been established. These results are compared with large-scale shell-model calculations in the full $\mathit{fp}$ shell.

The first results from the Stopped Beam RISING experimental campaign performed at the GSI laboratory in Darmstadt, Germany, are presented. RISING (Rare ISotope INvestigations at GSI) constitutes a major new experimental program in European nuclear structure physics research aimed at using relativistic‐energy, projectile‐fragmentation reactions to study nuclei with exotic proton‐to‐neutron ratios. This paper introduces the physics aims of the Stopped RISING collaboration and presents some technical details and initial results from experiments using the RISING array to study decays from metastable nuclear states in both proton and neutron‐rich nuclei.

The published experimental results on one‐proton and two‐proton radioactivity of 94Ag (21+) are reviewed and the doubts are discussed that were recently raised on these data on the basis of in‐beam γ‐ray spectroscopy of excited states of 92Rh.

This work is supported by the Science and Technology Facilities Council (STFC), UK, US Department of Energy, Office of Nuclear Physics, under Contract No. DEAC02-06CH11357 and DE-FG02-94ER40834, NSF grant PHY-1404442.

The yrast structure of 207Pb above the 13/2+ isomeric state has been investigated in deep-inelastic collisions of 208Pb and 208Pb at ATLAS, Argonne National Laboratory. New and previously observed transitions were measured using the Gammasphere detector array. The level scheme of 207Pb is presented up to ~ 6 MeV, built using coincidence and γ-ray intensity analyses. In addition, the spin and parity assignments of states were made, based on angular distributions and comparisons to shell model calculations.

A decay spectroscopy experiment was performed within the EURICA campaign at RIKEN in 2012. It aimed at the isomer and particle spectroscopy of excited states and ground states in the mass region below the doubly magic 100Sn. The N = Z nuclei 98In, 96Cd and 94Ag were of particular interest for the present study. Preliminary results on the neutron deficient nuclei 93Ag and 94Ag are presented. In 94Ag a more precise value for the half-life of the ground state’s superallowed Fermi transition was deduced. In addition the energy spectra of the mentioned decay could be reproduced through precise Geant4 simulations of the used active stopper SIMBA. This will enable us to extract Qβ values from the measured data. The decay of 93Ag is discussed based on the observed implantation-decay correlation events.

New excited states have been observed in the neutron deficient isotope Ag-98 following the Ni-58+Cr-50-->Te-108* heavy-ion reaction. One of these states may be interpreted as a maximum spin aligned state of the pi g(9/2)(-3) nu vg(7/2) configuration. Other possible interpretations within the nuclear shell model are discussed as well.

Gamma decays from excited states up to J(pi)=6() in the N=Z-2 nucleus Ni-54 have been identified for the first time. Level energies are compared with those of the isobars Co-54 and Fe-54 and of the cross-conjugate nuclei of mass A=42. The good but puzzling f(7/2) cross-conjugate symmetry in mirror and triplet energy differences is analyzed. Shell model calculations reproduce the new data but the necessary nuclear charge-dependent phenomenology is not fully explained by modern nucleon-nucleon potentials.

Jolie, J. Ilie, G. Reiter, P. Richard, A. Scherillo, A. Striepling, T. Warr, N. Banu, A. Becker, F. Bednarczyk, P. Doornenbal, P. Gerl, J. Grawe, H. Gorska, M. Kojouharov, I. Mandal, S. Saito, N. Saito, T. R. Wollersheim, H. -J. Mallion, S. Neyens, G. Turzo, K. Van Duppen, P. Vermeulen, N. Podolyak, Zs. Gelletly, W. Regan, P. H. Walker, P. M. Catford, W. N. Liu, Z. Williams, S. Blazhev, A. Lozeva, R. Detistov, P. Atanasova, L. Damyanova, G. Gil, D. Cortina Benlliure, J. Kurtukian Nieto, T. Caserejos, E. Daugas, J. M. Belier, G. Meot, V. Roig, O. Simpson, G. Tsekhanovich, I. S. Matea, I. Schwengner, R. Hass, M. Singh, B. S. Nara Chamoli, S. K. Goldring, G. Regev, I. Vaintraub, S. Balabanski, D. L. Lo Bianco, G. Gladnishki, K. Saltarelli, A. Petrache, C. Benzoni, G. Blasi, N. Bracco, A. Camera, F. Million, B. Leoni, S. Wieland, O. Maj, A. Kmiecik, M. Grebosz, J. Bednarczyk, P. Styczen, J. Lach, M. Meczynski, W. Mazurek, K. Pfutzner, M. Korgul, A. Ionescu-Bujor, M. Iordachescu, A. Zamfir, V. Jungclaus, A. Georgiev, G. Cullen, D. M. Freeman, S. J. Smith, A. G. Orlandi, R. Clark, R. M. Bentley, M. A. Hammond, G. Wadsworth, R. Buerger, A. Huebel, H. Rudolph, D. Fahlander, C. Simpson, J. Herzberg, R. D. Page, R. D. Nolan, P. Davidson, T. Woods, P. Bruce, A. M. Faestermann, T. Kruecken, R. Mach, H. Rubio, B. Algora, A.

The reduced transition probabilities B(E2;0{sup +}{yields}2{sub 1}{sup +}) of the neutron-rich {sup 74}Zn and {sup 70}Ni nuclei have been measured by Coulomb excitation in a {sup 208}Pb target at intermediate energy. These nuclei have been produced at Grand Accelerateur National d'Ions Lourds via interactions of a 60A MeV {sup 76}Ge beam with a Be target. The B(E2) value for {sup 70}Ni{sub 42} is unexpectedly large, which indicates that neutrons added above N=40 strongly polarize the Z=28 proton core. In the Zn isotopic chain, the steep rise of B(E2) values beyond N=40 continues up to {sup 74}Zn{sub 44}. The enhanced proton core polarization in {sup 70}Ni is attributed to the monopole interaction between the neutron in the g{sub 9/2} and protons in the f{sub 7/2} and f{sub 5/2} spin-orbit partner orbitals. This interaction could result in a weakening of magicity in {sup 78}Ni{sub 50}.

The population of metastable states produced in relativistic‐energy fragmentation of a 238U beam has been measured. For states with high angular momentum, I=17ℏ and I=21.5ℏ, a higher population than expected has been observed, with the discrepancy increasing with angular momentum. By considering two sources for the angular momentum, related to single‐particle and collective motions, a much improved description of the experimental results can be obtained. In addition, new results on the structure of 208Fr, 211Ra and 216Ac are reported.

High spin states in nuclei in the 208Pb region were populated in deep inelastic collisions of 136Xe and 208Pb projectiles with thick 208Pb targets at about 50 MeV above the Coulomb barrier. Prompt and prompt-delayed γ-ray coincidences were measured. Four new states above the 8+ isomer in 210Pb were found and spins and parities assigned from theoretical expectations. The results are discussed in the frame of shell model theory.

Excited states in the N=47 nucleus Rh-92 were populated via the fusion evaporation reaction Ni-58(Ca-40,alpha pn)Rh-92 at 180 MeV beam energy. A level scheme reaching up to about 7 MeV and probable spins of (19(+)) and (21(-)) was established and interpreted with the shell model in the (p(1/2), g(9/2)) model space.

The interpretation of the first backbending point in deformed rare earth nuclei as a crossing of the ground state band with a rotational band built on an aligned i132 neutron pair is rather well established. However, in terms of such a two-band mixing model one cannot understand the exclusive population of yrast states in and above the backbending point observed in Coulomb excitation experiments of neutron-rich, stable rare earth nuclei. To investigate this problem in more detail for the heavy Dy nuclei 160, 162Dy, an Incomplete Fusion experiment has been performed at the MPI fur Kernphysik in Heidelberg in order to investigate its suitability for studying these n-rich nuclei. A cross section of σ ≈ 150 mbarn for producing the nuclei with a spin distribution covering the first backbending region could be established.

The unstable neutron-deficient Sn-108 isotope has been studied in inverse kinematics by intermediate-energy Coulomb excitation using the RISING/FRS experimental setup at GSI. This is the highest Z nucleus studied so far with this method. Its reduced transition probability B (E2;0(g.s.)(+)-> 2(1)(+)) has been measured for the first time. The extracted B(E2) value of 0.230(57)e(2) b(2) has been determined relative to the known value in the stable Sn-112 isotope. The result is discussed in the framework of recent large-scale shell model calculations performed with realistic effective interactions. The roles of particle-hole excitations of the Sn-100 core and of the Z=50 shell gap for the E2 polarization are investigated.

Proton radioactivity from {sup 105}Sb has been reinvestigated at the GSI on-line mass separator. The nucleus was produced in the reaction {sup 50}Cr({sup 58}Ni,1p2n), and collected with a tape transport system. A double-sided Si strip detector was used for proton spectroscopy. The direct proton decay of {sup 105}Sb reported in an earlier experiment at Berkeley was not observed. The present data imply an upper limit {approx}10{sup -3} for the ground-state proton decay branching ratio for proton energies higher than 430 keV.