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Sökning: WFRF:(Steer S J)

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1.
  • Romagnoni, A, et al. (författare)
  • Comparative performances of machine learning methods for classifying Crohn Disease patients using genome-wide genotyping data
  • 2019
  • Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1, s. 10351-
  • Tidskriftsartikel (refereegranskat)abstract
    • Crohn Disease (CD) is a complex genetic disorder for which more than 140 genes have been identified using genome wide association studies (GWAS). However, the genetic architecture of the trait remains largely unknown. The recent development of machine learning (ML) approaches incited us to apply them to classify healthy and diseased people according to their genomic information. The Immunochip dataset containing 18,227 CD patients and 34,050 healthy controls enrolled and genotyped by the international Inflammatory Bowel Disease genetic consortium (IIBDGC) has been re-analyzed using a set of ML methods: penalized logistic regression (LR), gradient boosted trees (GBT) and artificial neural networks (NN). The main score used to compare the methods was the Area Under the ROC Curve (AUC) statistics. The impact of quality control (QC), imputing and coding methods on LR results showed that QC methods and imputation of missing genotypes may artificially increase the scores. At the opposite, neither the patient/control ratio nor marker preselection or coding strategies significantly affected the results. LR methods, including Lasso, Ridge and ElasticNet provided similar results with a maximum AUC of 0.80. GBT methods like XGBoost, LightGBM and CatBoost, together with dense NN with one or more hidden layers, provided similar AUC values, suggesting limited epistatic effects in the genetic architecture of the trait. ML methods detected near all the genetic variants previously identified by GWAS among the best predictors plus additional predictors with lower effects. The robustness and complementarity of the different methods are also studied. Compared to LR, non-linear models such as GBT or NN may provide robust complementary approaches to identify and classify genetic markers.
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6.
  • Lalkovski, S., et al. (författare)
  • Core-coupled states and split proton-neutron quasiparticle multiplets in Ag122-126
  • 2013
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:3, s. 034308-
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron-rich silver isotopes were populated in the fragmentation of a Xe-136 beam and the relativistic fission of U-238. The fragments were mass analyzed with the GSI Fragment Separator and subsequently implanted into a passive stopper. Isomeric transitions were detected by 105 high-purity germanium detectors. Eight isomeric states were observed in Ag122-126 nuclei. The level schemes of Ag-122,Ag-123,Ag-125 were revised and extended with isomeric transitions being observed for the first time. The excited states in the odd-mass silver isotopes are interpreted as core-coupled states. The isomeric states in the even-mass silver isotopes are discussed in the framework of the proton-neutron split multiplets. The results of shell-model calculations, performed for the most neutron-rich silver nuclei are compared to the experimental data.
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7.
  • Söderström, Pär-Anders, et al. (författare)
  • Spectroscopy of neutron-rich Dy-168,Dy-170 : Yrast band evolution close to the NpNn valence maximum
  • 2010
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 81:3, s. 034310-
  • Tidskriftsartikel (refereegranskat)abstract
    • The yrast sequence of the neutron-rich dysprosium isotope Dy-168 has been studied using multinucleon transfer reactions following collisions between a 460-MeV Se-82 beam and an Er-170 target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2(+) and 4(+) members of the previously measured ground-state rotational band of Dy-168 have been confirmed and the yrast band extended up to 10(+). A tentative candidate for the 4(+) -> 2(+) transition in Dy-170 was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of total Routhian surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed.
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8.
  • Wadsworth, R., et al. (författare)
  • THE NORTHWEST FRONTIER : SPECTROSCOPY OF N similar to Z NUCLEI BELOW MASS 100
  • 2009
  • Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 40:3, s. 611-620
  • Tidskriftsartikel (refereegranskat)abstract
    • The spectroscopy and structure of excited states of N similar to Z nuclei in the mass 70-100 region has been investigated using two techniques. In the A similar to 70-80 region fusion evaporation reactions coupled with the recoil-beta-tagging method have been employed at Jyvaskyla to study low-lying states in odd-odd N = Z nuclei. Results from these and other data for known odd-odd nuclei above mass 60 will be discussed. In the heavier mass 90 region a fragmentation experiment has been performed using the RIS-ING/FRS setup at GSI. This experiment was primarily aimed at searching for spin gap isomers in nuclei around A similar to 96. The objectives of the latter experiment will be discussed.
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9.
  • Craddock, Nick, et al. (författare)
  • Genome-wide association study of CNVs in 16,000 cases of eight common diseases and 3,000 shared controls
  • 2010
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 464:7289, s. 713-720
  • Tidskriftsartikel (refereegranskat)abstract
    • Copy number variants (CNVs) account for a major proportion of human genetic polymorphism and have been predicted to have an important role in genetic susceptibility to common disease. To address this we undertook a large, direct genome-wide study of association between CNVs and eight common human diseases. Using a purpose-designed array we typed,19,000 individuals into distinct copy-number classes at 3,432 polymorphic CNVs, including an estimated similar to 50% of all common CNVs larger than 500 base pairs. We identified several biological artefacts that lead to false-positive associations, including systematic CNV differences between DNAs derived from blood and cell lines. Association testing and follow-up replication analyses confirmed three loci where CNVs were associated with disease-IRGM for Crohn's disease, HLA for Crohn's disease, rheumatoid arthritis and type 1 diabetes, and TSPAN8 for type 2 diabetes-although in each case the locus had previously been identified in single nucleotide polymorphism (SNP)-based studies, reflecting our observation that most common CNVs that are well-typed on our array are well tagged by SNPs and so have been indirectly explored through SNP studies. We conclude that common CNVs that can be typed on existing platforms are unlikely to contribute greatly to the genetic basis of common human diseases.
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10.
  • Morales, A. I., et al. (författare)
  • beta -Delayed gamma -Ray Spectroscopy of Heavy Neutron Rich Nuclei "South" of Lead
  • 2009
  • Ingår i: Acta Physica Polonica B. - 0587-4254. ; 40:3, s. 867-870
  • Konferensbidrag (refereegranskat)abstract
    • Relativistic projectile fragmentation of a Pb-208 primary beam has been used to produce neutron-rich nuclei with proton-holes relative to the Z = 82 shell closure, i.e., "south" of Pb. beta-delayed gamma-ray spectroscopy allows to investigate the structural properties of such nuclei with A similar to 195 -> 205. The current work presents transitions de-exciting excited states in Au-204, which are the first spectroscopic information on this N = 125 isotone.
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11.
  • Wang, F., et al. (författare)
  • Reinvestigation of the excited states in the proton emitter Lu-151 : Particle-hole excitations across the N = Z=64 subshell
  • 2017
  • Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 96:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The excited states of the proton emitter Lu-151 were reinvestigated in a recoil-decay tagging experiment at the Accelerator Laboratory of the University of Jyvaskyla (JYFL). The level scheme built on the ground state of 151Lu was updated with five new y-ray transitions. Large-scale shell model calculations were carried out in the model space consisting of the neutron and proton orbitals 0g(7/2), Id(5/2), Id(3/2), 2s(1/2), and Oh(1/2) with the optimized monopole interaction in order to interpret the experimental level scheme of Lu-151. It is found that the excitation energies of states above the 27/2(-) and 23/2(+) isomeric levels in Lu-151 can be sensitive to excitations from g(7/2) and d(5/2) to single-particle orbitals above N = Z = 64.
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12.
  • Wang, F., et al. (författare)
  • Spectroscopic factor and proton formation probability for the d3/2 proton emitter 151mLu
  • 2017
  • Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 770, s. 83-87
  • Tidskriftsartikel (refereegranskat)abstract
    • The quenching of the experimental spectroscopic factor for proton emission from the short-lived d3/2 isomeric state in 151mLu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151mLu.
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13.
  • Al-Dahan, N., et al. (författare)
  • Nuclear Structure "Southeast" of 208Pb: Isomeric states in 208Hg and 209Tl
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:6
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 < 82 and N>126.
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14.
  • Morales, A. I., et al. (författare)
  • beta-delayed gamma-ray spectroscopy of Au-203,Au-204 and Pt200-202
  • 2013
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The beta decay of five heavy, neutron-rich nuclei, Pt-203,Pt-204 and Ir200-202, 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 Au-203,Au-204 and Pt200-202. The characteristic gamma rays for each nucleus have been determined using beta-delayed gamma-ray spectroscopy. Tentative level schemes, relative intensities, and apparent beta feedings are provided. These data are compared with shell-model calculations, which indicate a substantial contribution to the total beta strength from high-energy first-forbidden beta-decay transitions in this mass region.
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15.
  • Morales, A I, et al. (författare)
  • Half-Life Systematics across the N=126 Shell Closure: Role of First-Forbidden Transitions in the β Decay of Heavy Neutron-Rich Nuclei.
  • 2014
  • Ingår i: Physical Review Letters. - 1079-7114. ; 113:2
  • Tidskriftsartikel (refereegranskat)abstract
    • This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic ^{208}Pb. The lifetimes of the 126-neutron shell isotone ^{204}Pt and the neighboring ^{200-202}Ir, ^{203}Pt, ^{204}Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during β decay back to stability.
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16.
  • Al-Dahan, N., et al. (författare)
  • Multiple beta(-) decaying states in Re-194: Shape evolution in neutron-rich osmium isotopes
  • 2012
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:3
  • Tidskriftsartikel (refereegranskat)abstract
    • beta decays from heavy, neutron-rich nuclei with A similar to 190 have been investigated following their production via the relativistic projectile fragmentation of an E/A = 1 GeV Pb-208 primary beam on a similar to 2.5 g/cm(2) Be-9 target. The reaction products were separated and identified using the GSI FRagment Separator (FRS) and stopped in the RISING active stopper. gamma decays were observed and correlated with these secondary ions on an event-by-event basis such that gamma-ray transitions following from both internal (isomeric) and beta decays were recorded. A number of discrete, beta-delayed gamma-ray transitions associated with beta decays from Re-194 to excited states in Os-194 have been observed, including previously reported decays from the yrast I-pi = (6(+)) state. Three previously unreported gamma-ray transitions with energies 194, 349, and 554 keV are also identified; these transitions are associated with decays from higher spin states in Os-194. The results of these investigations are compared with theoretical predictions from Nilsson multi-quasiparticle (MQP) calculations. Based on lifetime measurements and the observed feeding pattern to states in Os-194, it is concluded that there are three beta(-)-decaying states in Re-194.
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17.
  • Caceres, L. S., et al. (författare)
  • Identification of Excited States in the N = Z Nucleus 82Nb
  • 2007
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 38:4, s. 1271-1275
  • Tidskriftsartikel (refereegranskat)abstract
    • Information on the first excited states in the N = Z = 41 nucleus Nb-82 sheds light on the competition of isospin T = 0 and T = 1 states in the A similar to 80 region. The measurement was performed at the GSI laboratory using fragmentation of a Ag-107 primary beam at 750 MeV/u on a 4 g/cm(2) Be-9 target. The fragments were separated and identified unambiguously in the FRagment Separator. Three excited states were observed and the half-life estimate for the isomeric state was extracted. A tentative spin assignment based on the isobaric analogue states systematics in the T-z = 1 nucleus Zr-82, and transition probabilities indicate T = 1 character of the first two excited states, and T = 0 for the isomeric state.
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18.
  • Pietri, S., et al. (författare)
  • First Results from the Stopped Beam Isomer RISING Campaign at GSI
  • 2007
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 38:4, s. 1255-1264
  • Tidskriftsartikel (refereegranskat)abstract
    • The first results from a series of experiments focused on the study of the internal structure of nuclei at the extremes of N:Z ratio using isomer spectroscopy are reported. These experiments represent the first of the Stopped Beam section of the Rare Isotopes Investigations at GSI (RISING) project. Exotic nuclei were synthesized using relativistic projectile fragmentation of similar to 500 -> 1000 MeV/u beams of Ag-107, Pb-208, Xe-136 and Ni-58, or fission of 750 MeV/u U-238 provided by the SIS synchrotron at GSI. A detailed description of the RISING stopped beam set up is given, together with a report of the performance of the associated gamma-ray spectrometer array. Selected results of the first experimental campaign are presented together with a discussion on the use of isomeric spectroscopy to study GeV range nuclear fragmentation. Details on future research plans of this collaboration are also outlined.
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19.
  • Podolyak, Zs., et al. (författare)
  • Isomeric Decay Studies Around 204Pt and 148Tb
  • 2007
  • Ingår i: The European Physical Journal. Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 150, s. 165-168
  • Tidskriftsartikel (refereegranskat)abstract
    • Relativistic energy projectile fragmentation of Pb-208 has been used to produce a range of exotic nuclei. The nuclei of interest were studied by detecting delayed gamma rays following the decay of isomeric states. Experimental information on the excited states of the neutron-rich N = 126 nucleus, Pt-204, following internal decay of two isomeric states, was obtained for the first time. In addition, decays from the previously reported isomeric I=27h and I=(49/2)h states in Tb-148 and Gd-147, respectively, have been observed. These isomeric decays represent the highest spin discrete states observed to date following a projectile fragmentation reaction, and opens further the possibility of doing 'high-spin physics' using this technique.
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20.
  • Regan, P. H., et al. (författare)
  • First Results from the Stopped RISING Campaign at GSI: The Mapping of Isomeric Decays in Highly Exotic Nuclei
  • 2007
  • Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. - 9780735413283 ; 899, s. 19-22
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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21.
  • Rudolph, Dirk, et al. (författare)
  • Exciting Isomers from the First Stopped-beam RISING Campaign
  • 2007
  • Ingår i: The European Physical Journal. Special Topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 150, s. 173-176
  • Tidskriftsartikel (refereegranskat)abstract
    • First results are reported from a major new initiative of experiments, which focus on nuclear structure studies at extreme isospin values by means of isomer spectroscopy. The experiments represent the first part of the so-called stopped-beam campaign within the Rare ISotope INvestigations at GSI (RISING) project. Time-correlated gamma decays from individually identified nuclear species have been measured, allowing the clean identification of isomeric decays in a wide range of exotic nuclei both at the proton drip-line and in heavy, neutron-rich systems. An overview of the experimental technique will be given, together with the performance of the new germanium detector array and future research plans for the collaboration.
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22.
  • Steer, S. J., et al. (författare)
  • Isomeric Decay Studies In Neutron-Rich N Approximate To 126 Nuclei
  • 2009
  • Ingår i: International Journal Of Modern Physics E-Nuclear Physics. - 0218-3013. ; 18:4, s. 1002-1007
  • Konferensbidrag (refereegranskat)abstract
    • Heavy neutron-rich nuclei were populated via relativistic energy fragmentation of a E/A= 1 GeV Pb-208 beam. The nuclei of interest were selected and identified by a fragment separator and then implanted in a passive plastic stopper. Delayed. 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.
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23.
  • Al-Dahan, N., et al. (författare)
  • Isomeric States In 208Hg And 209Tl Populated In Fragmentation Of 238U
  • 2009
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 40:3, s. 871-874
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 on a Be target. The preliminary analysis indicates the presence of previously unreported isomeric states in the N = 128 isotones Hg-208 and Tl-209.
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24.
  • Al-Dahan, N., et al. (författare)
  • Structure of N≥126 Nuclei Produced in Fragmentation of 238U
  • 2009
  • Ingår i: Proceedings of the 13th International Symposium on Capture Gamma‐Ray Spectroscopy and Related Topics. - : AIP. - 0094-243X. ; 1090, s. 145-148
  • Konferensbidrag (refereegranskat)abstract
    • The nuclear structure of neutron-rich N≥126 nuclei have been investigated following their production via relativistic projectile fragmentation of a E/A=l GeV 238U beam on a Be target. The cocktail of secondary beam products were separated and identified using the GSI FRagment Separator (FRS). The nuclei of interest were implanted in a high-granularity active stopper detector set-up consisting of 6 double sided silicon strip detectors. The associated gamma-ray transitions were detected with the RISING array, consisting of 15 Euroball cluster Ge-detectors. Time-correlated gamma decays from individually identified nuclear species have been recorded, allowing the clean identification of isomeric decays.
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25.
  • Alkhomashi, N., et al. (författare)
  • Beta(-)-Delayed And Isomer Spectroscopy Of Neutron-Rich Ta And W Isotopes
  • 2009
  • Ingår i: Acta Physica Polonica B. - 0587-4254. ; 40:3, s. 875-878
  • Konferensbidrag (refereegranskat)abstract
    • Decays of neutron-rich A similar to 190 nuclei have been studied following projectile fragmentation of a Pb-208 beam on a Be-9 target at the GSI Fragment Separator. Gamma-ray decays from previously reported isomeric states in Ta-188, W-190 and (192,193) Re were used as internal calibrations for the particle identification analysis, together with the identification of previously unreported isomeric decays in Ta-189 and W-191. The current work also identifies beta-delayed gamma rays following the decay of Ta-188 to W-188 for the first time.
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26.
  • Alkhomashi, N., et al. (författare)
  • beta(-)-delayed spectroscopy of neutron-rich tantalum nuclei: Shape evolution in neutron-rich tungsten isotopes
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:6
  • Tidskriftsartikel (refereegranskat)abstract
    • The low-lying structure of W-188,W-190,W-192 has been studied following beta decays of the neutron-rich mother nuclei Ta-188,Ta-190,Ta-192 produced following the projectile fragmentation of a 1-GeV-per-nucleon Pb-208 primary beam on a natural beryllium target at the GSI Fragment Separator. The beta-decay half-lives of Ta-188, Ta-190, and Ta-192 have been measured, with gamma-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion beta-gamma correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in W-188, W-190, and W-192, which highlight a change in nuclear shape at W-190 compared with that of lighter W isotopes. This evolution of ground-state structure along the W isotopic chain is discussed as evidence for a possible proton subshell effect for the A similar to 190 region and is consistent with maximization of the gamma-softness of the nuclear potential around N similar to 116.
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27.
  • Bacelar, A. M. Denis, et al. (författare)
  • Angular Momentum Population In Fragmentation Reactions
  • 2009
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 40:3, s. 889-892
  • Tidskriftsartikel (refereegranskat)abstract
    • Neutron-deficient nuclei with N = 126 have been populated following projectile fragmentation of a U-238 beam with energy 1 GeV/A. The decay of several previously reported isomers has been measured. This will allow us to calculate high-spin isomeric ratios and compare them with model calculations to allow a better understanding of the reaction mechanism.
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28.
  • Bianco, L., et al. (författare)
  • Discovery of W-157 and Os-161
  • 2010
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 690:1, s. 15-18
  • Tidskriftsartikel (refereegranskat)abstract
    • The nuclides W-157 and Os-161 have been discovered ill reactions of Ni-58 ion beams with a Cd-106 target. The Os-161 alpha-decay energy and half-life were 6890 +/- 12 keV and 640 +/- 60 mu s. The daughter W-157 nuclei beta-decayed with a half-life of 275 +/- 40 ms, populating both low-lying alpha-decaying states in Ta-157, which is consistent with a 7/2(-) ground state in W-157. Fine structure observed in the alpha decay of Os-161 places the lowest excited state in W-157 with 1(pi) = 9/2(-) at 318 +/- 30 key. The branching ratio of 5.5(-2.2)(+3.1)% indicates that Os-161 also has a 7/2(-) ground state. Shell-model calculations analysing the effects of monopole shifts and a tensor force on the relative energies of 2f(7/2) and 1h(9/2) neutron states in N = 83 isotones are presented. (C) 2010 Elsevier B.V. All rights reserved.
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29.
  • Caceres, L., et al. (författare)
  • Spherical proton-neutron structure of isomeric states in Cd-128
  • 2009
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 79:1, s. 011301-
  • Tidskriftsartikel (refereegranskat)abstract
    • The gamma-ray decay of isomeric states in the even-even nucleus Cd-128 has been observed. The nucleus of interest was produced both by the fragmentation of Xe-136 and the fission of U-238 primary beams. The level scheme was unambiguously constructed based on.. 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 p. interaction in overlapping orbitals for both proton and neutron holes.
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30.
  • Denis Bacelar, A.M., et al. (författare)
  • The population of metastable states as a probe of relativistic-energy fragmentation reactions
  • 2013
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 723:4–5, s. 302-306
  • Tidskriftsartikel (refereegranskat)abstract
    • Isomeric ratios have been measured for high-spin states in Po-198,200,206,208(84), At-208,209,210,211(85), Rn-210,211,212,213,214(86), Fr-208,211,212,213,214(87), Ra-210,211,212,214,215(88), and Ac-215(89) following the projectile fragmentation of a 1 AGeV U-238 beam by a Be-9 target at GSI Helmholtzzentrum fur Schwerionenforschung. The fragments were separated in the fragment separator (FRS) and identified by means of energy loss and time-of-flight techniques. They were brought to rest at the centre of the RISING gamma-ray detector array and intensities of gamma rays emitted in the decay of isomeric states with half-lives between 100 ns and 40 mu s and spin values up to 55/2 (h) over bar were used to obtain the corresponding isomeric ratios. The data are compared to theoretical isomeric ratios calculated in the framework of the abrasion-ablation model. Large experimental enhancements are obtained for high-spin isomers in comparison to expected values. (C) 2013 Elsevier B.V. All rights reserved.
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31.
  • Garnsworthy, A. B., et al. (författare)
  • Isomeric States in Neutron-deficient A~80-90 Nuclei Populated in the Fragmentation of 107Ag
  • 2009
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:6
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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32.
  • Garnsworthy, A. B., et al. (författare)
  • Isomeric States in the Light Tc Isotopes
  • 2007
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 38:4, s. 1265-1269
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 Ag-107 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, Tc-86, populated following the de-excitation of a microsecond isomer. Preliminary results of this analysis, as well as previously unobserved isomeric states in Tc-87,Tc-88. are reported.
  •  
33.
  • Garnsworthy, A B, et al. (författare)
  • Neutron-proton pairing competition in N = Z nuclei: Metastable state decays in the proton dripline nuclei Nb-82(41) and Tc-86(43)
  • 2008
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 660:4, s. 326-330
  • Tidskriftsartikel (refereegranskat)abstract
    • The low-lying structures of the self-conjugate (N = Z) nuclei Nb-82(41)41 and Tc-86(43)43 have been investigated using isomeric-decay spectroscopy following the projectile fragmentation of a Ag-107 beam. These represent the heaviest odd-odd N = Z nuclei in which internal decays have been identified to date. The resulting level schemes shed light on the shape evolution along the N = Z line between the doubly-magic systems Ni-56(28) and Sn-100(50) and support a preference for T = 1 states in T-z = 0 odd-odd nuclei at low excitation energies associated with a T = 1 neutron-proton pairing gap. Comparison with Projected Shell Model calculations suggests that the decay in Nb-82 may be interpreted as an isospin-changing K isomer.
  •  
34.
  • Gorska, M., et al. (författare)
  • Evolution of the N=82 Shell Gap below 132Sn Inferred from Core Excited States in 131In
  • 2009
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 672:4-5, s. 313-316
  • Tidskriftsartikel (refereegranskat)abstract
    • The gamma-ray decay of ail excited state in In-131, the one proton hole neighbor of the doubly magic (132)sn has been measured. A high-spin, core-excited isomer with T-1/2 = 630(60) us was identified following production by both relativistic fragmentation of a Xe-136 beam and fission Of a U-238 beam. This state deexcites by a single gamma-ray branch of 3782(2) keV from which direct evidence for the size of the N = 82 shell gal) 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. (C) 2009 Elsevier B.V. All rights reserved.
  •  
35.
  • Grodner, E., et al. (författare)
  • Hindered Gamow-Teller Decay to the Odd-Odd N=Z 62Ga: Absence of Proton-Neutron T=0 Condensate in A=62
  • 2014
  • Ingår i: Physical Review Letters. - 1079-7114. ; 113:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, Jπ=0+ ground state of Ge62 into excited states of the odd-odd N=Z nucleus Ga62. The experiment is performed at GSI Helmholtzzentrum für Schwerionenforschung with the Ge62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14) ms is measured for the Ge62 ground state. Six excited states of Ga62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical predictions of the interacting shell model and the quasiparticle random phase approximation. The absence of any sizable low-lying Gamow-Teller strength in the reported beta-decay experiment supports the hypothesis of a negligible role of coherent T=0 proton-neutron correlations in Ga62.
  •  
36.
  • Molina, F., et al. (författare)
  • Tz=-1 → 0 β-Decays of 54Ni, 50Fe, 46Cr, and 42Ti and Comparison With Mirror (3He,t) Measurements
  • 2015
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the β decay of the Tz=−1, f7/2 shell nuclei Ni54, Fe50, Cr46, and Ti42 produced in fragmentation reactions. The proton separation energies in the daughter Tz=0 nuclei are relatively large (≈4–5 MeV) so studies of the γ rays are essential. The experiments were performed at GSI as part of the Stopped-beam campaign with the RISING setup consisting of 15 Euroball Cluster Ge detectors. From the newly obtained high precision β-decay half-lives, excitation energies, and β branching ratios, we were able to extract Fermi and Gamow-Teller transition strengths in these β decays. With these improved results it was possible to compare in detail the Gamow-Teller (GT) transition strengths observed in beta decay including a sensitivity limit with the strengths of the Tz=+1 to Tz=0 transitions derived from high resolution (3He,t) reactions on the mirror target nuclei at RCNP, Osaka. The accumulated B(GT) strength obtained from both experiments looks very similar although the charge exchange reaction provides information on a broader energy range. Using the “merged analysis” one can obtain a full picture of the B(GT) over the full Qβ range. Looking at the individual transitions some differences are observed, especially for the weak transitions. Their possible origins are discussed.
  •  
37.
  • Naqvi, F., et al. (författare)
  • Isomer spectroscopy of (127)Cd
  • 2010
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 82:3, s. 034323-
  • Tidskriftsartikel (refereegranskat)abstract
    • The spin and configurational structure of excited states of (127)Cd, the two-proton and three-neutron hole neighbor of (132)Sn, has been studied. An isomeric state with a half-life of 17.5(3) mu s was populated in the fragmentation of a (136)Xe beam on a (9)Be target at a beam energy of 750 MeV/u. Time distributions of the delayed gamma transitions and gamma gamma coincidence relations were exploited to construct a decay scheme. The observed yrast (19/2)(+) isomer is proposed to have dominant configurations of nu(h(11/2)(-3))pi(g(9/2)(-1), p(1/2)(-1)), nu(h(11/2)(-2)d(3/2)(-1))pi(g(9/2)(-2)), and nu(h(11/2)(-2), s(1/2)(-1))pi(g(9/2)(-2)) and to decay by two competing stretched M2 and E3 transitions. Experimental results are compared with the isotone (129)Sn. The new information provides input for the proton-neutron interaction and the evolution of neutron hole energies in nuclei around the doubly magic (132)Sn core.
  •  
38.
  • Podolyak, Zs., et al. (författare)
  • Proton-hole excitation in the closed shell nucleus Au-205
  • 2009
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 672:2, s. 116-119
  • Tidskriftsartikel (refereegranskat)abstract
    • The neutron-rich N = 126 nucleus Au-205 has been populated following the relativistic energy projectile fragmentation of E/A = 1 GeV Pb-208, and studied via charged-particle decay spectroscopy. An internal decay with a transition energy of 907(5) keV and a half-life of T-1/2 = 6(2) s has been identified through the observation of the corresponding K and L internal conversion electron lines. The 907 keV energy level corresponds to the pi h(11/2)(-1) proton-hole state and decays both internally into the pi d(3/2)(-1) ground-state and via beta decay into Hg-205. The obtained data provides information on the evolution of single-proton hole energies which are vital inputs of shell model descriptions for nuclei around the Pb-208(82)126 doubly magic core. (C) 2009 Elsevier B.V. All rights reserved.
  •  
39.
  • Wadsworth, R., et al. (författare)
  • Spin-gap Isomer in 96Cd
  • 2012
  • Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 381:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Evidence has been obtained for the existence of the long predicted 16+ spin-gap isomer in 96Cd. The decay of the isomer was identified and studied following the use of an 850 MeV/u beam of 124Xe impinging on a Be target and the fragment recoil separator at the GSI Laboratory. Gamma decays from the fragments were detected using the RISING gamma ray array, in its stopped beam configuration, plus a silicon active stopper. The data obtained have been compared with shell model predictions, which indicate that the isoscalar neutron-proton interaction plays a key role in the formation of the isomer.
  •  
40.
  • Doornenbal, P., et al. (författare)
  • RISING: Gamma‐ray Spectroscopy with Radioactive Beams at GSI
  • 2007
  • Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X. - 9780735413283 ; 891, s. 99-107
  • Konferensbidrag (refereegranskat)abstract
    • The Rare Isotope Spectroscopic INvestigation at GSI (RISING) project is a major pan‐European collaboration. Its physics aims are the studies of exotic nuclear matter with abnormal proton‐to‐neutron ratios compared with naturally occurring isotopes. RISING combines the FRagment Separator (FRS) which allows relativistic energies and projectile fragmentation reactions with EUROBALL Ge Cluster detectors for γ spectroscopic research. The RISING setup can be used in two different configurations. Either the nuclei of interest are investigated after being stopped or the heavy ions hit a secondary target at relativistic energies and the thereby occurring excitations are studied. For the latter case, MINIBALL Ge detectors and the HECTOR array are used in addition. Example achievements of the Fast Beam setup are presented and compared to various shell model calculations, while for the Stopped Beam setup initial results are shown.
  •  
41.
  • Farrelly, G. F., et al. (författare)
  • Revision of the K-Isomer in 190W
  • 2009
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 40:3, s. 885-888
  • Tidskriftsartikel (refereegranskat)abstract
    • Gamma rays from the decay of an isomer in W-190(116) have been observed following projectile fragmentation of a 1 GeV per nucleon Pb-208 beam. An earlier experiment indicated decay from a (10(-)) isomer to the ground state rotational band. Improved statistics have enabled gamma coincidence and time-difference measurements to be made which alter the previous interpretation. Blocked BCS calculations have also been used together with reduced hindrance factors to indicate possible values of spin-parity for the isomer.
  •  
42.
  • Ketelhut, S., et al. (författare)
  • gamma-Ray Spectroscopy at the Limits : First Observation of Rotational Bands in Lr-255
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:21, s. 212501-
  • Tidskriftsartikel (refereegranskat)abstract
    • The rotational band structure of Lr-255 has been investigated using advanced in-beam gamma-ray spectroscopic techniques. To date, Lr-255 is the heaviest nucleus to be studied in this manner. One rotational band has been unambiguously observed and strong evidence for a second rotational structure was found. The structures are tentatively assigned to be based on the 1/2(-)[521] and 7/2(-)[514] Nilsson states, consistent with assignments from recently obtained alpha decay data. The experimental rotational band dynamic moment of inertia is used to test self-consistent mean-field calculations using the Skyrme SLy4 interaction and a density-dependent pairing force.
  •  
43.
  •  
44.
  • Myalski, S., et al. (författare)
  • Isomeric Ratio for the I=8+ Yrast State in 96Pd Produced in the Relativistic Fragmentation of 107Ag
  • 2007
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 38:4, s. 1277-1282
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the preliminary results from a study of the decay of the I-pi = 8(+) T-1/2 = 2 mu s isomer in Pd-96 performed as part of the Stopped-Beam RISING campaign within the Rare Isotope Investigation at GSI (RISING). The Pd-96 ions were produced following the projectile fragmentation of a 750 MeV per nucleon Ag-107 primary beam. The reaction products were separated and identified by the in-flight method using the GSI Fragment Separator. The residues of interest were stopped in a perspex stopper surrounded by an array of 15, seven-element germanium Cluster detectors. One of the goals of the current work is to investigate the population of high-spin states produced projectile fragmentation reactions using isomeric ratio measurements to infer information on the angular momentum population distribution. In this short contribution the method and results of determining the isomeric ratio for the I-pi = 8(+) microsecond isomer in Pd-96 nucleus are presented.
  •  
45.
  • Myalski, S., et al. (författare)
  • Isomeric Ratios For Nuclei With Z=62-67 And A=142-152 Produced In The Relativistic Fragmentation Of Pb-208
  • 2009
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 40:3, s. 879-883
  • Tidskriftsartikel (refereegranskat)abstract
    • Isomeric states in nuclei with Z = 62-67 and A = 142-152 produced in the fragmentation of the relativistic (1 GeV/nucleon) Pb-208 beam were investigated. Isomeric ratios were determined for 10 isomeric states. Significant differences between theoretical and experimental values were observed.
  •  
46.
  • Myalski, S., et al. (författare)
  • Study of Isomer Production Rates for A=142-152 and Z=62-67 in Fragmentation of a Relativistic 208Pb Beam
  • 2012
  • Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254. ; 43:2, s. 253-259
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated nuclear fragmentation reactions of a relativistic Pb-208 beam. Ten isomeric states for nuclei with A = 142-152 and Z = 62-67 were observed. Measured isomeric ratios were compared, together with values from other experiments, with prediction of theoretical models. The discrepancies between the experimental and theoretical values were discussed in terms of transitions by-passing the isomer that are not included in the models.
  •  
47.
  • Page, R. D., et al. (författare)
  • alpha decay of Re-159 and proton emission from Ta-155
  • 2007
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 75:6, s. 061302-
  • Tidskriftsartikel (refereegranskat)abstract
    • The alpha decay of Re-159 has been observed for the first time in reactions of 300 MeV Ni-58 ions with an isotopically enriched Cd-106 target. The Re-159 ions were separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The alpha decay emanates from the proton-emitting pi h(11/2) state in Re-159 with an energy of E-alpha=6776 +/- 26 keV and a branching ratio of 7.5 +/- 3.5%. This alpha decay populates a state in the closed neutron shell nucleus Ta-155, which decays by emitting 1444 +/- 15 keV protons with a half-life of 2.9(-1.1)(+1.5) ms. These values are consistent with the emission of the proton from a pi h(11/2) orbital. These results fit in with the systematics of proton and alpha-particle separation energies in the region, but disagree with the previously reported decay properties of Ta-155.
  •  
48.
  • Page, R. D., et al. (författare)
  • Probing single-particle structures beyond the proton drip line
  • 2007
  • Ingår i: Proton Emitting Nuclei and Related Topics. - : American Institute of Physics (AIP). - 9780735404755 ; , s. 137-142
  • Konferensbidrag (refereegranskat)abstract
    • Single-particle energies have been investigated in the closed neutron shell proton emitter 155Ta. The 155Ta nuclei were populated through the α decay of 159Re, which has been observed for the first time. The 159Re nuclei were produced in reactions of 300 MeV 58Ni ions with an isotopically enriched 106Cd target, separated in-flight using the RITU separator and implanted into the GREAT spectrometer. The 159Re α decay emanates from the proton-emitting πh11/2 state and populates a state in 155Ta which decays by the emission of a proton from a πh 11/2 orbital. The results fit in with the systematics of proton and α-particle separation energies in the region, but disagree with the previously reported decay properties of 155Ta.
  •  
49.
  • Pietri, S., et al. (författare)
  • First observation of the decay of a 15(-) seniority v=4 isomer in Sn-128
  • 2011
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 83:4, s. 044328-
  • Tidskriftsartikel (refereegranskat)abstract
    • Isomeric states in the semimagic Sn128-130 isotopes were populated in the fragmentation of a Xe-136 beam on a Be-9 target at an energy of 750 A.MeV. The decay of an isomeric state in Sn-128 at an excitation energy of 4098 keV has been observed. Its half live has been determined to be T-1/2 = 220(30) ns from the time distributions of the delayed gamma rays emitted in its decay. gamma gamma coincidence relations were analyzed in order to establish the decay pattern of the newly established state toward the known (7(-)) and (10(+)) isomers at excitation energies of 2092 and 2492 keV, respectively. Based on a comparison with results of state-of-the-art shell-model calculations the new isomeric state is proposed to have the nu h(11/2)(-3)d(3/2)(-1) configuration with the four neutron holes in Sn-132 maximally aligned to a total spin of I-pi = 15(-).
  •  
50.
  • Podolyak, Zs., et al. (författare)
  • Structure of Neutron-rich Nuclei Around the N=126 Closed Shell; the Yrast Structure of 205Au up to Spin-parity I = (19/2+)
  • 2009
  • Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 42:3, s. 489-493
  • Konferensbidrag (refereegranskat)abstract
    • 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(+)).
  •  
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