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Search: L773:0375 9474 OR L773:1873 1554 > (1990-1999)

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1.
  • Arve, Per, et al. (author)
  • The NN-1, π and ΔN-1 delta decay modes in the nuclear medium
  • 1994
  • In: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 572:3-4, s. 600-620
  • Journal article (peer-reviewed)abstract
    • The dependence of the Δ-width on the Δ-decay channels is studied in the nuclear medium. We calculate the decay of the delta into a nucleon and a general pisobar mode consisting of NN-1-, π- and dN-1-modes. For the case of no width of the Δ in the pisobar we present partial contributions to the Δ-width from the Δ-decay channels: Δ→N+NN-1, Δ→N+π and Δ→N+ΔN-1. Results for a self-consistent treatment of the Δ-width in the pisobar is presented. The self-consistent treatment only modifies the results with no width in the pisobar to a small extent. It is found that NN-1 channel is not only dominating the decay at low energies of the Δ-resonance but at high densities (ρ>1.5ρ0) this channel also dominates the decay at higher energies. Qualitative agreement with inclusive and exclusive (p,n) and (3He,T) experiments is achieved
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2.
  • Bark, R A, et al. (author)
  • Bandcrossings in Os-171
  • 1999
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 646:4, s. 399-413
  • Journal article (peer-reviewed)abstract
    • The nucleus Os-171 has been populated using the reaction Sn-116(Ni-58,2pn). Four new bands are identified, and the previously known bands are extended in spin, to a maximum of 53/2 (h) over bar. One- and three-quasiparticle configurations are identified, and beta, gamma, and octupole configurations are assigned tentatively. The effects of a possible intruder configuration on the negative parity bands are tested using band-mixing calculations.
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3.
  • Bark, R A, et al. (author)
  • Coexistence of triaxial and prolate shapes in Ir-171
  • 1999
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 657:2, s. 113-133
  • Journal article (peer-reviewed)abstract
    • Excited states in Ir-171 have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method, The ground-state band has a structure consistent with an h(11/2) proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation, Band-mixing calculations are performed for Ir171-175. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for Ir171-179 using the code "Ultimate Cranker". Dipole bands were also observed, but tilted axis cranking calculations suggest that they are associated with a collective rotation.
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4.
  • CEDERKALL, J, et al. (author)
  • 1ST OBSERVATION OF EXCITED-STATES IN SB-108
  • 1995
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 581:1, s. 189-204
  • Journal article (peer-reviewed)abstract
    • A spectroscopic study of Sb-108 has been carried out as a part of a larger experiment where in total twenty-nine different residual nuclei were identified. This study gives the first information on excited levels in this nucleus. A low-lying two-quasi-particle multiplet together with some of the higher lying levels are discussed within the framework of the nuclear shell model. A rotational, strongly coupled, band is identified as, most likely, being built on the deformed pig9/2(-1) nuh11/2 configuration in accordance with total routhian surface calculations. Tentative spins and parities are presented as well as B(M1)/B(E2) ratios for some of the transitions in the strongly coupled band.
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5.
  • Cederwall, Bo, et al. (author)
  • HIGH-SPIN STATES IN BA-121 AND DEFORMATION-DEPENDENT ALIGNMENTS
  • 1991
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 529:2, s. 410-428
  • Journal article (peer-reviewed)abstract
    • The high-spin structure of 121Ba has been investigated by in-beam gamma-ray spectroscopic techniques. Rotational bands based on the h11/2, g7/2 and tentatively d5/2 quasineutron configurations have been established. The alignments of h11/2 protons and neutrons are identified at HBAR-omega-c = 0.35-0.40 MeV in the h11/2 and g7/2 bands whereas an alignment occurs at HBAR-omega-c = 0.29 MeV in the (tentatively) d5/2 band. B(M1)/B(E2) ratios were extracted and contributed to the configuration assignments. The results are interpreted within the cranked mean-field approach.
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6.
  • Cederwall, Bo, et al. (author)
  • SIGNATURE INVERSION IN CS-120 - EVIDENCE FOR A RESIDUAL PN INTERACTION
  • 1992
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 542:3, s. 454-478
  • Journal article (peer-reviewed)abstract
    • High-spin states have been observed in the odd-odd isotope 120Cs in S-32-induced reactions. The previously known band is extended to higher spin and several new bands are identified. Band-head configurations have been inferred by comparing the band properties with known bands in the odd nuclei 121Cs and 121Ba. A remarkable signature inversion is observed in the pi-h11/2 x nu-h11/2 band. The experimental data are compared with calculations made within the total routhian surface model and the two-particle plus triaxial rotor model. It is concluded that a significant residual pn interaction rather than triaxiality is responsible for the signature inversion phenomenon in the pi-h11/2 x nu-h11/2 band of 120Cs.(~)[GRAPHICS]
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7.
  • FAHLANDER, C, et al. (author)
  • IN-BEAM SPECTROSCOPY OF TE-110
  • 1994
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 577:3-4, s. 773-785
  • Journal article (peer-reviewed)abstract
    • The neutron-deficient nucleus Te-110 has been investigated by in-beam spectroscopic methods using the NORDBALL multi-detector array. Except for the energy of one level observed in alpha-decay, excited states in Te-110 were previously unknown. The level scheme constructed from gamma gamma-coincidence relationships is presented with tentative spin assignments up to I-pi = 21(-). Above spin 8(+) the yrast states have negative parity. They are most likely the members of a band predominantly based on the nu(h(11/2)g(7/2)) two-quasiparticle configuration. A band crossing is observed at I-pi approximate to 17(-). It is suggested to be caused by the alignment of two h(11/2) neutrons. The cranked shell model correctly predicts the spin alignment, but fails to reproduce the observed band crossing frequency, possibly because of octupole effects.
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8.
  • HILDINGSSON, L, et al. (author)
  • HIGH-SPIN PHENOMENA IN OS-174
  • 1992
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 545:4, s. 871-888
  • Journal article (peer-reviewed)abstract
    • High-spin states of 174Os have been investigated by means of the (Nd(S, 4n)Os)-Nd-146-S-32-Os-174 reaction using the ESSA30 multidetector system. The decay is dominated by the ground-state positive-parity band, two negative-parity 4- and 5- bands and another band starting at spin 9. Deformed shell-model calculations have been carried out to interpret the observed band structures. The role of the strongly shape-driving, non-aligned, pi-h9/2 configuration in the low-spin region of the ground-state band is discussed. The first band crossing is interpreted as due to the nu-i13/2 alignment. The two lowest side-bands are understood in terms of coupling to octupole excitations.
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9.
  • JERRESTAM, D, et al. (author)
  • COLLECTIVE EXCITATIONS IN CD-106
  • 1994
  • In: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 571:2, s. 393-412
  • Journal article (peer-reviewed)abstract
    • High Spin states in 106Cd were populated by the reactions Zr-94(O-17, 5n) and Ge(S-32, 4n) at 80 MeV and at 148 MeV, respectively. The gamma-decay was studied by gamma-spectroscopic methods using the Nordball multi-detector army. Protons and alpha-particles were detected in particle detector system, thus selecting the neutron channel. The experiment included gamma-ray yields, gammagamma-coincidences and gamma-ray angular relation measurements. Collective bands extending up to spin 26+, 20- and 21-, have been observed in 106Cd. A new lifetime Of 11(-3)+6 ns for the 16+ state at 7118.7 keV has been found. Both total Routhian surfaces and spin diabatic surfaces have been calculated and used for assigning quasiparticle configurations to the bands. The (+, 0) band is assigned as a nuh11/2(2) configuration below I = 16+ and at higher spins suggested to be built on a pig9/2(2)nuh11/2(2) configuration. The large hindrance observed for the decay from the 16+ state supports the latter assignment. With the alignment of the nuh11/12(2) pair the deformation is predicted to change from (epsilon2,gamma) = (0.13,-2-degrees) to (0.17, 4-degrees). The configuration of the negative parity bands is assigned as either a nuh11/2(1)d5/2(1) or a nuh11/2(1)(g7/2xd5/2)1, With (epsilon2, gamma) = (0.14,9-degrees.
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10.
  • Jonsson, K, et al. (author)
  • Collective excitations and band termination in Nb-85
  • 1999
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 645:1, s. 47-60
  • Journal article (peer-reviewed)abstract
    • High-spin states in Nb-85 were studied using the GAMMASPHERE Ge detector array and the MICROBALL charged-particle detector system. Three gamma-ray cascades with collective rotational characteristics were observed. One of the bands exhibits a forking at the top, most likely reflecting the termination of one branch into a favoured non-collective, near spherical state. The data are interpreted in terms of cranked Strutinsky-type calculations.
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11.
  • Juutinen, S, et al. (author)
  • Coexistence of collective and quasiparticle structures in Sn-106 and Sn-108
  • 1997
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 617:1, s. 74-90
  • Journal article (peer-reviewed)abstract
    • New levels in the neutron deficient nuclei Sn-106 and Sn-108 have been investigated by using the NORDBALL detector array combined with charged particle and neutron detectors. The excited structures are discussed in terms of collectivity and the shell model. The excitations are interpreted to be based on d5/2, g7/2 and h(11/2) both for protons and neutrons and g(9/2) for protons. The systematical behaviour of the specific states in the Sn isotopes is studied in the mass range of A = 106-118.
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12.
  • Kownacki, J, et al. (author)
  • High-spin studies of the neutron deficient nuclei In-103, In-105, In-107, and In-109
  • 1997
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 627:2, s. 239-258
  • Journal article (peer-reviewed)abstract
    • High-spin states of the isotopes 103,105,107,109In have been investigated using in-beam γ-ray spectroscopic methods. Results from three different experiments are presented. Targets of 54Fe, 50Cr, and 92Mo were bombarded by a 270 and 261 MeV 58Ni beam and by a 95 MeV 19F beam, respectively. Reaction channel separation was achieved with a charged-particle detector array and in the first two experiments also with a 1π neutron detector system. As a result of these experiments the level schemes of 103,105,107,109In were significantly extended. Excited states of these odd-A indium isotopes are discussed within the framework of the nuclear shell model and the hole-core coupling scheme. The systematics of excited states of light odd-A indium isotopes is also discussed.
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13.
  • LIDEN, F, et al. (author)
  • ALIGNMENT PROCESSES IN CS-119, CS-121 AND CS-123
  • 1992
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 550:2, s. 365-390
  • Journal article (peer-reviewed)abstract
    • Rotational band structures have been observed in the odd-A Cs isotopes 119Cs, 121Cs and 123Cs. The previously known bands have been extended to higher spin values and several new bands have been established. Alignments of both h11/2 protons and neutrons are seen. Of special interest are the alignment frequencies in the (tentative) [422]3/2+ and [404]9/2+ bands which indicate a configuration-dependent proton pairing. Furthermore, the variation of the interaction strength at the first band crossing in the h11/2 bands does not follow the standard cranked-shell-model predictions. This feature is in line with previous systematic observations of alignment processes in high-j intruder bands, and might infer an additional band mixing due to a neutron-proton interaction.(~)[GRAPHICS]
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14.
  • Palacz, M, et al. (author)
  • In-beam gamma-ray spectroscopy of Co-56
  • 1997
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474 .- 1873-1554. ; 627:1, s. 162-174
  • Journal article (other academic/artistic)abstract
    • Excited states of Co-56 were studied in the reaction Al-27(S-32,2p1n) Co-56. The NORDBALL array with a Neutron Wall and a Silicon Ball was employed. The excited states were interpreted in terms of particle-hole excitations with respect to the doubly magic
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15.
  • Persson, J, et al. (author)
  • In-beam gamma-ray spectroscopy of Cd-102
  • 1997
  • In: Nuclear Physics A. - : ELSEVIER SCIENCE BV. - 0375-9474 .- 1873-1554. ; 627:1, s. 101-118
  • Journal article (peer-reviewed)abstract
    • Neutron deficient nuclei close to 100Sn have been studied using the NORDBALL Ge-detector array together with ancillary particle detectors. Evaporation residues from the compound nucleus 108Te were identified with charged particle and neutron detectors. In this paper a considerable extension of the level scheme of the nucleus 102Cd is presented. The strongest cascade of the new level scheme reveals an irregular sequence of dipole transitions above Iπ = 10+ extending up to spin 17. A strongly populated rather regular side band consisting of four quadrupole transitions ranging from spin 9 to spin 17 was also discovered. This band was tentatively assigned negative parity. Shell model calculations were performed and a very good agreement with the experimental results was found. The excited states could successfully be interpreted as neutron particle and proton hole excitations with respect to the doubly closed core 50100Sn50.
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16.
  • Rudolph, D, et al. (author)
  • Multiparticle-hole states of high spin in N < 50, A ≈ 90 nuclei : 1. The transitional nucleus 4389Tc46
  • 1995
  • In: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 587:1, s. 181-201
  • Journal article (peer-reviewed)abstract
    • High spin states in the nucleus 89Tc have been studied via the fusion evaporation reaction 58Ni(40Ca,2αp)89Tc at 180 MeV beam energy. The NORDBALL γ-ray spectrometer equipped with auxiliary detectors for light particle selection was used to measure γγ- and particle-γγ coin-cidences. Some 60 transitions were placed into a level scheme comprising 38 levels reaching up to 9.2 MeV excitation energy and a possible spin of . The level scheme is compared to those of neighbouring nuclei and interpreted in terms of the spherical shell model. The calculations were performed with different sets of parameters within a restricted , , and configuration space. States above 2.3 MeV excitation energy are well reproduced by shell model calculations based on an empirical residual interaction, whereas collective excitations are suggested to contribute to the wave functions of lower lying states.
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17.
  • SEWERYNIAK, D, et al. (author)
  • IN-BEAM STUDY OF IN-102, IN-104 AND IN-106
  • 1995
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 589:1, s. 175-200
  • Journal article (peer-reviewed)abstract
    • Proton-rich odd-odd In isotopes have been investigated by in-beam spectroscopic methods using the NORDBALL detector array. A Ni-58 beam with an energy of 270 MeV was used to bombard a Fe-54 target. Separation of different reaction channels was achieved with a 4 pi charged-particle multi-detector set-up together with a 1 pi neutron detector wall placed in the forward direction. Excited states of the In-102 nucleus were identified for the first time as well as a set of negative-parity states in In-104. In In-106 the information about positive- and negative-parity states has been extended. The nuclei are discussed within the framework of the nuclear shell model, the interacting boson-fermion-fermion model and the systematics of the heavier odd-odd indium isotopes.
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18.
  • TORMANEN, S, et al. (author)
  • COMPETING PROTON AND NEUTRON ALIGNMENTS IN NEUTRON-DEFICIENT XE-NUCLEI
  • 1994
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 572:2, s. 417-458
  • Journal article (peer-reviewed)abstract
    • High-spin structures of the neutron-deficient Xe-117, Xe-118, Xe-120 isotopes have been studied by in-beam gamma-ray spectroscopic techniques. The final nuclei have been identified by means of charged-particle detectors. Collective rotational bands based on the neutron d5/2, 97/2 and h11/2 configurations have been identified in Xe-117. In the even Xe-118 and Xe-120 nuclei several new side bands were observed and the previously known bands were extended. The present level schemes include two positive-parity bands constructed to high spin in Xe-118, whereas in Xe-120 three such bands were observed. In order to explain these bands, both proton and neutron (h11/2)2 alignments, as well as the shape degree of freedom, have to be invoked. The possible occurrence of a gammaS-band is addressed and a pronounced structural change for more heavy Xe-isotopes is discussed. All negative-parity side bands are interpreted in terms of proton two-quasiparticle excitations. The experimental data are compared with total routhian surface calculations.
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19.
  • JUTTINEN, S, et al. (author)
  • GAMMA-RAY SPECTROSCOPY OF CD-110
  • 1994
  • In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 573:2, s. 306-332
  • Journal article (peer-reviewed)abstract
    • The nucleus Cd-110 has been studied using the C-13 and O-18 induced reactions and the NORDBALL multi-detector array. The yrast band was observed to I(pi) = 28+ and a large number of side bands were identified. The h11/2 neutrons were found to play a dominant role in the observed rotational structures. The weakly populated yrast 3187 keV 8+ state is interpreted as arising from the proton g9/2(-2) configuration. Collective bands, where the band members are connected by DELTAI = 1 transitions and where the DELTAI = 2 transitions are not observed, are also reported. These bands are interpreted to have prolate configurations involving both the h11/2 neutrons and the g9/2 protons. The experimental data are discussed in terms of the total routhian surface and cranked shell model calculations.
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20.
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21.
  • Adamovich, M.I., et al. (author)
  • Charged particle multiplicity and pseudorapidity density distributions in 16O-, 28Si- and 197Au-induced nuclear interactions at 14.6 and 11.6A GeV/c
  • 1995
  • In: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 593:4, s. 535-549
  • Journal article (peer-reviewed)abstract
    • Pseudorapidity density and multiplicity distributions of charged particles produced in heavy-ion collisions at the BNL AGS have been studied. The multiplicity distributions and pseudorapidity distributions of shower particles in Au-induced interactions are presented and compared with model predictions from RQMD, FRITIOF and VENUS. It is shown that the widths of the pseudorapidity distributions of produced particles in central collisions are independent of the interacting system. The results from EMU01 have been compared, and found to agree, with the results from two other heavy-ion experiments, E802 and E814.
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22.
  • Afanasjev, A. V., et al. (author)
  • The coexistence of the intruder vi13/2, superdeformed and terminating bands in the A ∼ 135 mass region
  • 1996
  • In: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 608:2, s. 176-201
  • Journal article (peer-reviewed)abstract
    • The configuration-dependent shell-correction approach with the cranked Nilsson potential is employed for a systematic investigation of the high-spin spectra of the nuclei in the A ∼ 135 (Z = 57-61, N = 72-78) mass region, where superdeformed bands have been observed. Main attention is paid to the coexistence of intruder νi13/2, superdeformed and terminating bands in the yrast region. Recent developments of the formalism allow the identification of the high-j orbitals in each N-shell, for example, the g9/2 orbitals in the N = 4 shell, after the diagonalization of the cranked Nilsson potential. This turns out to be quite important for the understanding of the high collectivity of the observed bands. It is shown that the equilibrium deformation of the superdeformed bands is strongly dependent on the number of the proton holes in the g9/2 orbitals. With increasing neutron number above N = 75, the intruder νi13/2 bands are calculated triaxial. Especially for Z = 57, but also for higher proton numbers, we calculate some coexistent oblate non-collective states which are yrast for specific spin values at I ≥ 40h.
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23.
  • Aleksandrov, D., et al. (author)
  • Invariant mass spectrum and alpha-n correlation function studied in the fragmentation of He-6 on a carbon target
  • 1998
  • In: Nuclear Physics A. - 0375-9474. ; 633:2, s. 234-246
  • Journal article (peer-reviewed)abstract
    • Momentum distributions and invariant mass spectra from the breakup of He-6 ions with an energy of 240 MeV/u interacting with a carbon target have been studied. The data were used to extract information about the reaction mechanism which is influenced by the structure of He-6. It is found that the dominant reaction mechanism is a two-step process: knock out of one neutron followed by the decay of the He-5 resonance. The shape of the (alpha+n) two-body invariant mass spectrum is interpreted as mainly reflecting the 5He ground state which is a J(pi) = 3/2(-) resonance. However, no evidence for correlations between cu particles and neutrons is observed in the momentum widths of the distributions. It is demonstrated that a combined analysis of the two-body invariant mass spectrum and an appropriate correlation function may be used to determine the properties of the intermediate resonance. (C) 1998 Elsevier Science B.V.
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24.
  • Anne, R., et al. (author)
  • Exclusive and Restricted-Inclusive Reactions Involving the Be-11 One-Neutron Halo
  • 1994
  • In: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 575:1, s. 125-154
  • Journal article (peer-reviewed)abstract
    • Reactions of a 41 MeV/u beam of the radioactive halo nucleus Be-11 have been studied with a counter telescope coupled to an array of neutron detectors covering angles up to 97-degrees. The technique allows to determine single-neutron inclusive and exclusive angular distributions. The targets (Be, Ti and Au) were chosen to illustrate the relative roles played by nuclear and Coulomb mechanisms. The channels leading to Be-10, the dissociation channels, correspond to impact parameters larger than the sum of the radii of the target and the Be-10 core. It is shown that for the dissociation process it is possible to account almost quantitatively for the integral, single- and double-differential cross sections from models without free parameters including the Coulomb, Serber and Glauber (diffraction-dissociation) mechanisms. The neutron distributions from the nondissociative reaction channels show little individuality and it is convenient to group them together as the channel ''neutron plus anything different from Be-10''. We refer to these as ''restricted-inclusive'' reactions. These seem to be a promising tool for obtaining accurate information on the halo wave function in momentum coordinates.
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25.
  • Axelsson, L., et al. (author)
  • Beta decay of Ar-31
  • 1998
  • In: Nuclear Physics A. - 0375-9474. ; 634:4, s. 475-496
  • Journal article (peer-reviewed)abstract
    • A complete study of Ar-31 beta decay has been made by high-resolution charged-particle and gamma-ray spectroscopy. Beta-delayed radiation was detected by an array of three charged-particle detectors and a large-volume germanium detector. Fifteen new energy levels were discovered in Cl-31. The beta-strength distribution, measured to 14.5 MeV, is compared with a shell-model calculation in the full sd space. The quenching of the Gamow-Teller strength and the isospin impurity of the IAS in Cl-31 are discussed. (C) 1998 Published by Elsevier Science B.V.
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26.
  • Axelsson, L., et al. (author)
  • Two-proton emission in the decay of Ar-31
  • 1998
  • In: Nuclear Physics A. - 0375-9474. ; 628:3, s. 345-362
  • Journal article (peer-reviewed)abstract
    • Several beta-delayed two-proton branches were observed in the decay of Ar-31, the most intense ones proceeding through the isobaric analogue state (IAS) in Cl-31. The mechanism of the two-proton emission is studied via the energy and angular distributions of the two protons, Simultaneous emission of the two protons fits the present data well, sequential decays might also describe them. Independent of the decay mechanism, a spin of 5/2 for the IAS is suggested, An improved limit on the direct two-proton emission fi om the ground state of Ar-31 is presented, (C) 1998 Elsevier Science B.V.
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27.
  • Borge, M. J. G., et al. (author)
  • Probing the Li-11 halo structure through beta-decay into the Be-11(*) (18 MeV) state
  • 1997
  • In: Nuclear Physics A. - 0375-9474. ; 613:3, s. 199-208
  • Journal article (peer-reviewed)abstract
    • An experimental study of beta-delayed charged particles (H, He, Be) from Li-11 shows a beta-feeding to an excited state at 18.15(15) MeV in Be-11 with a large Gamow-Teller strength, B-GT greater than or equal to 1.6. Branching ratios and reduced widths of 2-, 3- and 5- particle decay channels of this state are extracted, A strong suppression of the neutron branch from the 18 MeV state to the Be-10(g.s.) is observed, We suggest that the measured partial width may be sensitive to the (p(1/2))(2) component in the Li-11 halo, A rough estimate indicates that the (p(1/2))(2) component is not the dominant one in the halo wave-function.
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28.
  • Borge, M. J. G., et al. (author)
  • Study of Charged-Particles Emitted in the Beta-Decay of He-6,He-8
  • 1993
  • In: Nuclear Physics A. - 0375-9474. ; 560:2, s. 664-676
  • Journal article (peer-reviewed)abstract
    • The beta-delayed charged particle spectra from He-6 and He-8 were measured with a telescope consisting of a gas counter and a Si surface barrier detector. Beta-delayed deuterons and tritons are emitted in the two cases with branching ratios of (7.6 +/- 0.6) x 10(-6), E(d) > 350 keV and (8.0 +/- 0.5) x 10(-3), respectively. Both spectra present anomalies that must be due to the special structure of these nuclei (an alpha core surrounded by several neutrons).
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29.
  • Borge, M. J. G., et al. (author)
  • The Decay of Ar-31
  • 1990
  • In: Nuclear Physics A. - 0375-9474. ; 515:1, s. 21-30
  • Journal article (peer-reviewed)
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30.
  • De Angelis, G., et al. (author)
  • Collective Excitations in the Vicinity of N=Z
  • 1999. - 1 SUPPL. 1
  • In: Proceedings INPC 1998. - 0375-9474. ; 654, s. 659-662
  • Conference paper (peer-reviewed)abstract
    • In our contribution to the INPC98 conference we reported on the experimental investigation of high spin collective states in medium and heavy mass N≈Z nuclei at LNL. The main purpose is to set light on the role of the proton-neutron interaction in the collective behavior of the nucleus. In medium mass N=Z nuclei, in contrast with the stable nuclei, valence protons and neutrons occupy the same orbitals and one may expect a reinforcement of neutron-proton T=0 (np) pairing correlations[1]. In this interesting subject, the medium mass N=Z=36 72Kr has been studied and completely reported in [2]. In this proceedings we will concentrate in unpublished results concerning the onset of collectivity on nearly spherical nuclei in the 100Sn region. In nuclei with Z=50 and Z=49 dipole bands have been found indicating the presence of "Magnetic Rotation" [3].
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31.
  • Grevy, S., et al. (author)
  • Core-breakup reactions of the halo nuclei Be-11 and Li-11: momentum distributions and shadow effects
  • 1999
  • In: Nuclear Physics A. - 0375-9474. ; 650:1, s. 47-61
  • Journal article (peer-reviewed)abstract
    • The halo nuclei Be-11 and Li-11 have been studied in core-breakup reactions where the halo neutrons are expected to be released without a major distortion due to the reaction. The widths of the halo-neutron momentum distributions have been extracted in coincidence with He fragments, Gamma = 32 +/- 4 MeV/c, and Li fragments, Gamma = 42 +/- 4 MeV/c for Be-11 and with He fragments, Gamma =42+/-6 MeV/c for Li-11. The Be-11 breakup gives a very low neutron multiplicity of 0.38+/-0.09 which is a manifestation of the shadowing of the neutron in the core-breakup reaction. This value can be understood from a simple theoretical calculation, which also accounts for the observed transverse momentum widths at small angles. (C) 1999 Elsevier Science B.V.
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32.
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33.
  • Honkanen, A., et al. (author)
  • Fine structure in the beta-delayed proton decay of Ar-33
  • 1996
  • In: Nuclear Physics A. - 0375-9474. ; 611:1, s. 47-55
  • Journal article (peer-reviewed)abstract
    • Low-energy beta-delayed protons from Ar-33 have been measured for the first time, The data reveal states, which, despite unfavourable barrier penetrability values, strongly decay to the first excited 2(+) state in S-32. The observation is discussed in terms of the standard shell model, A natural explanation is provided by the large spectroscopic amplitudes, involving s(1/2) and d(3/2) orbitals, as well as the l = 0 barrier penetrability, favouring the decay to the 2(+) state.
  •  
34.
  • Mukha, I., et al. (author)
  • Super-strong beta-decay of Li-11 into Be-11* (18 MeV) state: A probe for halo p-wave component?
  • 1997
  • In: Nuclear Physics A. - 0375-9474. ; 616:1-2, s. C201-C207
  • Conference paper (peer-reviewed)abstract
    • An experimental study of beta-delayed charged particles (H, He, Be), neutrons and gamma-rays that follow the Li-11 beta-decay, clearly indicates a beta-feeding to an exited state at 18.1 MeV in Be-11 with a large Gamow-Teller strength, B-GT greater than or equal to 1.0. The large strength of this beta-transition implies a broad overlap of the Be-11* state at 18.1 MeV and the ground state of Li-11. The deduced width of this resonance is similar or equal to 1 MeV. A strong suppression of the branch from 18.1 MeV state into the Be-10+n channel is observed. This branch, with the largest decay energy, has a partial width less than 1% of the total width. A centrifugal barrier consideration fails to explain this effect. A possible consequence of the observed effect for the Li-11 structure is that the admixture of (p(1/2))(2) configuration in Li-11 might be small.
  •  
35.
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36.
  • Proff, S, et al. (author)
  • Electromagnetic polarizabilities of nucleons bound in 40Ca, 16O and 4He
  • 1999
  • In: Nuclear Physics A. - 0375-9474. ; 646:1, s. 67-82
  • Journal article (peer-reviewed)abstract
    • Differential cross sections for elastic scattering of photons have been measured for 40Ca at energies of 58 and 74 MeV and for 16O and 4He at 61 MeV, in the angular range from 45° to 150°. Evidence is obtained that there are no significant in-medium modifications of the electromagnetic polarizabilities except for those originating from meson exchange currents.
  •  
37.
  • Schnack-Petersen, H, et al. (author)
  • Superdeformed triaxial bands in Lu-163,165
  • 1995
  • In: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 594:2, s. 175-202
  • Journal article (peer-reviewed)abstract
    • An experimental investigation of the nucleus 165Lu, using the reactions 138Ba(31P,4n) 165Lu and 150Sm(19F,4n) 165Lu at beam energies of E = 155 and 95 MeV, respectively, has been performed. Among other additions to the existing level scheme, a new band, with transition energies almost identical to a strongly deformed (β2 0.42) πi13/2[660 1/2+] band recently discovered in 163Lu has been established. A theoretical analysis of the structure of the two Lu isotopes, 165Lu and 163Lu is carried out by detailed calculations of total potential energy surfaces for specific configurations. By a diabatic treatment of crossings specific proton configurations as πi13/2[660 1/2+] are identified throughout the deformation space and as a function of spin. It is found as a general feature that well deformed local minima of considerable nonaxial symmetry coexist with a normal deformed global minimum. The depth of these local minima depend on configuration. The structure of the different global and local minima found in these surfaces are analysed and discussed in terms of occupation of available basis configurations and their orientation relative to the rotation axis. The strongly deformed minima are found to belong to a group of superdeformed triaxial structures, expected to appear at low energies for certain favourable combinations of proton and neutron numbers.
  •  
38.
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39.
  •  
40.
  • Zinser, M., et al. (author)
  • Invariant-mass spectroscopy of Li-10 and Li-11
  • 1997
  • In: Nuclear Physics A. - 0375-9474. ; 619:1-2, s. 151-176
  • Journal article (peer-reviewed)abstract
    • Break-up of secondary Li-11 ion beams (280 MeV/nucleon) on C and Pb targets into Li-9 and neutrons is studied experimentally. Cross sections and neutron multiplicity distributions are obtained, characterizing different reaction mechanisms. Invariant-mass spectroscopy for Li-11 and Li-10 is performed. The E1 strength distribution, deduced from electromagnetic excitation of Li-11 up to an excitation energy of 4 MeV comprises similar to 8% of the Thomas-Reiche-Kuhn energy-weighted sumrule strength. Two low-lying resonance-like structures are observed for Li-10 at decay energies of 0.21(5) and 0.62(10) MeV, the former one carrying 26(10)% of the strength and likely to be associated with an s-wave neutron decay. A strong di-neutron correlation in Li-11 can be discarded. Calculations in a quasi-particle RPA approach are compared with the experimental results for Li-10 and Li-11. (C) 1997 Elsevier Science B.V.
  •  
41.
  • Aas, AJ, et al. (author)
  • Enhanced and quenched B(E1) transition rates between parity doublet bands in Ra-227
  • 1996
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 611:2-3, s. 281-314
  • Journal article (peer-reviewed)abstract
    • The fast timing beta gamma gamma(t) method has been used to measure level lifetimes in the parity doublet bands in Ra-227 populated in the beta(-) decay of Fr-227. In particular, T-1/2 = 254(9) ps, 236(30) ps, less than or equal to 41 ps and 16(13) ps hav
  •  
42.
  • Aas, AJ, et al. (author)
  • Quenched E1 transition rates in Th-231
  • 1999
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 654:3-4, s. 499-522
  • Journal article (peer-reviewed)abstract
    • The fast timing beta gamma gamma(t) method has been used to measure lifetimes of the low-lying levels in Th-231 populated in the beta(-) decay of Ac-231. The half-life of the K-pi = 5/2(-) band-head at 185.7-keV was measured as T-1/2 = 1073(79) ps, yieldi
  •  
43.
  • Bilger, R, et al. (author)
  • CELSIUS as an eta factory
  • 1997
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 626:1-2, s. 93C-96C
  • Journal article (peer-reviewed)abstract
    • The WASA project at the CELSIUS storage ring is being prepared for high-luminosity experiments to study rare decays of light mesons, in particular the eta meson. The CELSIUS ring together with the newly developed pellet target will serve as an efficient e
  •  
44.
  • Bright, TB, et al. (author)
  • Radiative proton capture to discrete states in C-12 at 98 and 176 MeV
  • 1996
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 603:1, s. 1-22
  • Journal article (other academic/artistic)abstract
    • A high-resolution magnetic pair spectrometer for medium energy photons has been used for studies of the exclusive (p, gamma) reaction on B-11 at 98 and 176 MeV, We present angular distributions of the differential cross section for transitions to the grou
  •  
45.
  • Bright, TB, et al. (author)
  • Radiative proton capture to discrete states in N-31 at 98 and 176 MeV
  • 1997
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 621:3, s. 754-766
  • Journal article (other academic/artistic)abstract
    • A high resolution magnetic pair spectrometer for medium energy photons has been used for studies of the exclusive (p,gamma) reaction on C-12 at 98 and 176 MeV, We present angular distributions of the differential cross section for transitions to the groun
  •  
46.
  • Faldt, Goran, et al. (author)
  • A comparison of np -> d eta and np -> np eta production rates
  • 1996
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 604:4, s. 441-454
  • Journal article (peer-reviewed)abstract
    • It is shown that in the impulse approximation the ratio of the near-threshold np --> {np}(I=0) eta to np --> d eta production rates depends weakly upon the form of the production operator and can be estimated using low-energy neutron-proton dynamics. The
  •  
47.
  • FALDT, Goran, et al. (author)
  • THE REACTION PD-]HE-3-ETA NEAR-THRESHOLD
  • 1995
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 587:4, s. 769-786
  • Journal article (peer-reviewed)abstract
    • The cross section and deuteron tenser analysing power of the reaction pd-->He-3 eta are studied near threshold in a two-step model, where a pion beam, created in a NN-->d pi reaction on one of the nucleons in the target deuteron, is converted into an eta-
  •  
48.
  • Fraile, LM, et al. (author)
  • Octupole correlations in Ra-229
  • 1999
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 657:4, s. 355-390
  • Journal article (peer-reviewed)abstract
    • The structure of Ra-229 has been studied in the beta(-) decay of Fr-229. Spins and parities have been determined from the conversion electron measurements, while half-lives for the 137.5, 142.7, 168.8, 213.0 and 479.0 keV levels have been measured in the
  •  
49.
  • Ghetti, R, et al. (author)
  • Characterization of nuclear sources via two-neutron intensity interferometry
  • 1999
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 660:1, s. 20-40
  • Journal article (peer-reviewed)abstract
    • The neutron energy spectrum and the two-neutron correlation function have been measured for the E/A = 45 MeV Ni + Al reaction in order to assess the space-time characteristics of the neutron emitting source. When comparing the data to a statistical model,
  •  
50.
  • Gulda, K, et al. (author)
  • Quadrupole deformed and octupole collective bands in Ra-228
  • 1998
  • In: NUCLEAR PHYSICS A. - : ELSEVIER SCIENCE BV. - 0375-9474. ; 636:1, s. 28-46
  • Journal article (peer-reviewed)abstract
    • Spins and parities for collective states in Ra-228 have been determined from conversion electron measurements with a mini-orange beta spectrometer. The fast-timing beta gamma gamma(t) method has been used to measure lifetimes of T-1/2 = 550(20) ps and 181
  •  
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