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1.
  • Jonson, Björn, 1941-, et al. (författare)
  • Decay of (86)Rn-210(124) to Levels in (85)at-210(125)
  • 1973
  • Ingår i: Physica Scripta. - 0031-8949. ; 7:4, s. 147-159
  • Tidskriftsartikel (refereegranskat)abstract
    • The decay of 210Rn to 210At has been investigated. Gamma rays were recorded in singles and coincidence using Ge(Li) detectors. Conversion electrons were studied with a Si(Li) detector and a double focusing magnetic spectrometer. Internal conversion coefficients have been deduced and several transition multipolarities have been determined. A decay scheme is presented and spin assignments are made. The electron capture decay from 210Rn has been found to proceed mainly to three levels in 210At: 2 280.8 keV (0-, (1-)), 1 525.5 keV (1+) and 1 488.6 keV (1+), with log ft values <5.5 (L-capture), 7.0, and 7.1, respectively. The nature of these states is discussed. The feeding to the 2 281 keV level is interpreted as a first forbidden beta decay due to either a πh9/2 → νg9/2 or a πs1/2 → νp1/2 transition leading to a [π(h9/23)ν(g9/2p 1/2-2)]0- or a [π(h9/24s1/2-1) ν(p1/2-1)]0 state, respectively. The 1 526 and 1 489 keV states may arise from the π(h9/22|≠0h9/2) ν(f5/2-1) and possibly the π(h9/22f7/2) ν(f5/2-1) configurations. The π(h9/23)ν(p1/2-1) doublet is found at 0 and 72.7 keV. Two levels assigned as members of the π(h9/22|0 h9/2)ν(f5/2-1) configuration are found at 530.9 keV (3+) and 496.1 keV (4+).
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2.
  • Akkoyun, S., et al. (författare)
  • AGATA-Advanced GAmma Tracking Array
  • 2012
  • Ingår i: Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment. - 0168-9002. ; 668, s. 26-58
  • Tidskriftsartikel (refereegranskat)abstract
    • The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a gamma ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of gamma-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer.
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3.
  • Aksyutina, Yu, et al. (författare)
  • Lithium isotopes beyond the drip line
  • 2008
  • Ingår i: Physics Letters B. - 0370-2693. ; 666:5, s. 430-434
  • Tidskriftsartikel (refereegranskat)abstract
    • The unbound isotopes 10Li, 12Li and 13Li have been observed after nucleon-knockout reactions at relativistic energies with 11Li and 14Be beams impinging on a liquid hydrogen target. The channels , and were analysed in the ALADIN-LAND setup at GSI. The 10Li data confirm earlier findings, while the 12Li and 13Li nuclei were observed for the first time. The relative-energy spectrum shows that the ground state of 12Li can be described as a virtual s-state with a scattering length of -13.7(1.6) fm. A broad energy spectrum was found for the channel. Based on the assumption that the relative-energy spectrum is dominated by a correlated background presumably stemming from initial correlations in the 14Be ground-state, evidence for a 13Li resonance at 1.47(31) MeV above the threshold with a width around 2 MeV has been found.
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4.
  • Aksyutina, Y., et al. (författare)
  • Momentum profile analysis in one-neutron knockout from Borromean nuclei
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693. ; 718:4-5, s. 1309-1313
  • Tidskriftsartikel (refereegranskat)abstract
    • One-neutron knockout reactions from Borromean nuclei are analyzed using a profile function analysis technique. The profile function, which is derived as the square root of the variance of the measured fragment + neutron momenta as a function of their relative energy, is shown to be very sensitive to the angular momentum of the knocked out neutron. Three cases are studied here: He-7, where the profile function analysis shows a presence of (s(1/2))(2) component in the He-8 ground-state wave-function, Li-10, where the presence of a 11(2)% d-wave contribution to the relative energy spectrum above 1.5 MeV is found and, finally, the presence of a major s contribution around 0.5 MeV relative energy in the Be-13 case and that the observed decay to the Be-12 2(+) state originates in a d state in Be-13.
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5.
  • Aksyutina, Yuliya, et al. (författare)
  • Properties of the 7He ground state from 8He neutron knockout
  • 2009
  • Ingår i: Physics Letters B. - 0370-2693. ; 679:3, s. 191-196
  • Tidskriftsartikel (refereegranskat)abstract
    • The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the α+n relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a Iπ=1/2− state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.
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6.
  • Aksyutina, Y., et al. (författare)
  • Structure of the unbound nucleus Be-13: One-neutron knockout reaction data from Be-14 analyzed in a holistic approach
  • 2013
  • Ingår i: Physical Review C. - 0556-2813. ; 87:6
  • Tidskriftsartikel (refereegranskat)abstract
    • At the ALADIN-LAND setup at GSI the unbound nucleus Be-13 has been produced in one-neutron knockout reactions from a 304 MeV/nucleon relativistic beam of Be-14 ions impinging on a liquid hydrogen target. An analysis of the data including all available information about Be-13, and in particular recent data from a similar experiment performed at RIKEN, has been performed. A consistent description is reached. It is found that the excitation spectrum is dominated by s-waves at low energy, which solves problems from previous seemingly contradictory interpretations. A possible interference between two s-states in Be-13 is also discussed. The results indicate that the ground-state wave function of Be-14 is dominated by valence neutrons in the s-shell contributing with 60-75% of the total neutron knockout cross section.
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7.
  • Aksyutina, Y., et al. (författare)
  • Study of the Be14 continuum: Identification and structure of its second 2+ state
  • 2013
  • Ingår i: Physical Review Letters. - 0031-9007. ; 111:24
  • Tidskriftsartikel (refereegranskat)abstract
    • The coupling between bound quantum states and those in the continuum is of high theoretical interest. Experimental studies of bound drip-line nuclei provide ideal testing grounds for such investigations since they, due to the feeble binding energy of their valence particles, are easy to excite into the continuum. In this Letter, continuum states in the heaviest particle-stable Be isotope, Be14, are studied by employing the method of inelastic proton scattering in inverse kinematics. New continuum states are found at excitation energies E*=3.54(16) MeV and E*=5.25(19) MeV. The structure of the earlier known 21+ state at 1.54(13) MeV was confirmed with a predominantly (0d5/2)2 configuration while there is very clear evidence that the 22+ state has a predominant (1s1/2, 0d 5/2) structure with a preferential three-body decay mechanism. The region at about 7 MeV excitation shows distinct features of sequential neutron decay via intermediate states in Be13. This demonstrates that the increasing availability of energetic beams of exotic nuclei opens up new vistas for experiments leading towards a new understanding of the interplay between bound and continuum states. © 2013 American Physical Society.
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8.
  • Alcorta, M., et al. (författare)
  • Nuclear Structure of C-12 from Break-up Studies in Complete Kinematics
  • 2009
  • Ingår i: Nuclear Structure and Dynamics '09. - 0094-243X. ; 1165, s. 27-30461
  • Konferensbidrag (refereegranskat)abstract
    • A complete kinematics study of the B-10(He-3,p alpha alpha alpha) and B-11(He-3,d alpha alpha alpha) reactions has been performed to study the multi-particle break-up of C-12 resonances above the triple-alpha threshold. Four-particle coincidence detection gives us complete information on the direction and energy of the individual alpha particles from the decay of C-12, allowing us to extract new information on the structure of C-12 which we shall present in this contribution. We have observed gamma de-excitation of the T=1 15.11 MeV resonance using charged particle detectors, and have constructed Dalitz plots of the individual resonances in C-12 using the complete kinematics information of the alpha particles which come from their break-up.
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9.
10.
  • Aleksandrov, D., et al. (författare)
  • Halo excitations in fragmentation of He-6 at 240 MeV/u on carbon and lead targets
  • 2000
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 669:1-2, s. 51-64
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissociation of a 240 MeV/u beam of He-6, incident on carbon and lead targets, has been studied in kinematically complete experiments to investigate low-lying excitation modes in the halo nucleus He-6. It is shown that alignment effects characterize the inelastic scattering and allow an unambiguous assignment of the spin of a narrow resonance observed in the excitation energy spectrum. The differential cross sections for the He-6 inelastic scattering on carbon and lead targets were deduced from the measured moments of the two neutrons and the a-particle. An analysis of these distributions shows that quadrupole and, possibly, monopole excitations characterize the hadronic interaction, while the dipole mode is dominating in Coulomb dissociation. Neither theoretically predicted new resonance states in He-6 nor nuclear excitation of a dipole mode were found. Direct evidence has been obtained for strong suppression of Coulornb post-acceleration in direct Coulomb breakup in a lead target.
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