| 1. |
- Ghetti, Roberta, et al.
(författare)
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Particle emission time sequence in intermediate energy heavy ion reactions
- 2003
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Ingår i: Nuclear Physics, Section A. - 0375-9474 .- 1873-1554. ; 721, s. 313-316
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Tidskriftsartikel (refereegranskat)abstract
- The CHIC Collaboration has performed a series of simultaneous pp, np and nn fermion interferometry experiments in order to study the space-time evolution of the emission sources in intermediate energy heavy ion reactions. Furthermore, when correlations of non-identical particles are available, additional model independent information on the emission chronology of the particles is obtained. In this contribution, after reviewing the method to determine the order of emission of non-identical particles, we discuss the emission chronology of neutrons and protons from the E/A = 45 MeV Ni-58 + Al-27 reaction and from the E/A = 60 MeV Ar-36 + Al-27 reaction, shown here for the first time.
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| 2. |
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| 3. |
- Sohler, D, et al.
(författare)
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Neutron Excitations Across the N=50 Shell Gap in 102In
- 2002
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Ingår i: Nuclear Physics, Section A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 708:3-4, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.
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| 4. |
- Ahrens, J., et al.
(författare)
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Results from the AMANDA telescope
- 2003
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Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 721, s. C545-C548
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Tidskriftsartikel (refereegranskat)abstract
- We present results from the AMANDA high energy neutrino telescope located at the South Pole. They include measurements of the atmospheric neutrino flux, search for UHE point sources, and diffuse sources producing electromagnetic/hadronic showers at the detector or close to it.
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| 5. |
- Andreyev, A. N., et al.
(författare)
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The discovery of a prolate-oblate-spherical shape triple of spin 0(+) states in the atomic nucleus Pb-186
- 2001
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 682, s. 482C-486C
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Tidskriftsartikel (refereegranskat)abstract
- Two excited J(pi)=0(+) states in Pb-186 populated in the a-decay of Po-190 have been identified through alpha -particle/conversion electron coincidences in an experiment at the velocity filter SHIP. The parent Po-190 nuclei have been produced in the Nd-142(Cr-52,4n)Po-190 complete fusion reaction, alpha -particle energies and branching ratios have been measured and hindrance factors were deduced. The observed states have been interpreted as the band heads of the known prolate and (yet unobserved) oblate rotational bands in Pb-186.
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| 6. |
- Fritioff, Tomas, et al.
(författare)
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Shedding light on the Mercury Mass Discrepancy by weighing Hg52+ ions in a Penning trap
- 2003
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Ingår i: Nuclear Physics A. - : Elsevier Science B.V.. - 0375-9474 .- 1873-1554. ; 723:1-2, s. 3-16
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Tidskriftsartikel (refereegranskat)abstract
- In their nuclear tables Audi and Wapstra have pointed out a serious mass discrepancy between their extrapolated values for the mercury isotopes and those from a direct measurement by the Manitoba group. The values deviate by as much as 85 ppb from each other with claimed uncertainties of about 16 and 7 ppb, respectively. In order to decide which values are correct the masses of the 198Hg and 204Hg isotopes have been measured in the Stockholm Penning trap mass spectrometer SMILETRAP using 52+ ions. This charge state corresponds to a filled Ni electron configuration for which the electron binding energy can be accurately calculated. The mass values obtained are 197.966 768 44(43) u for 198Hg and 203.973 494 10(39) u for 204Hg. These values agree with those measured by the Manitoba group, with a 3 times lower uncertainty. This measurement was made possible through the implementation of a cooling technique of the highly charged mercury ions during charge breeding in the electron beam ion source used for producing the Hg52+ ions.
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| 7. |
- Gudowski, Waclaw
(författare)
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Transmutation of nuclear waste
- 2000
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 663, s. 169C-182C
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Tidskriftsartikel (refereegranskat)
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| 8. |
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| 9. |
- Henriksson, Krister O. E., et al.
(författare)
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Pion decay widths of D mesons
- 2001
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 686, s. 355-378
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Tidskriftsartikel (refereegranskat)abstract
- The pionic decay rates of the excited L = 0, 1 D mesons are calculated with a Hamiltonian model within the Framework of the covariant Blankenbecler-Sugar equation. The interaction between the light quark and charm antiquark is described by a linear scalar confining and a screened one-gluon exchange interaction. The decay widths of the D* mesons obtain a contribution from the exchange current that is associated with the linear scalar confining interaction. If this contribution is taken into account along with the single-quark approximation, the calculated decay rates of the charged D* mesons are readily below the current empirical upper limits if the axial coupling constant of the light constituent quarks is taken to be g(A)(q) = 0.87, but reach the empirical upper limits if g(A)(q) = 1. With the conventional values for g(A)(q), the calculated widths of the D-1 and D-2* mesons fall somewhat below the experimental lower limits, leaving room for other decay modes as well, such as pi pi decay. The unrealistically large contribution from the axial charge operator to the calculated pion decay width of the D-1 meson is suppressed by taking into account the exchange charge effects that are associated with the scalar linear confining and vector one-gluon exchange interactions. The predicted values for the pionic widths uf the hitherto undiscovered L = 1 D-1* and D-0* mesons are found to be smaller than previous estimates.
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| 10. |
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| 11. |
- Jonsell, Svante, et al.
(författare)
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Low energy hydrogen-antihydrogen collisions
- 2000
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 663-664, s. 959C-962C
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Tidskriftsartikel (refereegranskat)abstract
- The ground-state interaction potential between hydrogen and antihydrogen has been calculated within the Born-Oppenheimer approximation. Cross sections for rearrangement and annihilation in flight have been determined. Implications for cooling of antihydro
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| 12. |
- Joss, D. T., et al.
(författare)
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Identification of excited states in Os-167 and Os-168 : shape coexistence at extreme neutron deficiency
- 2001
-
Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 689:04-mar, s. 631-654
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in the very neutron-deficient isotopes Os-167 and Os-168 have been observed using the reaction Sn-112(Ni-58, 2pxn). The JUROSPHERE gamma -ray spectrometer array was used in conjunction with the RITU gas-filled recoil separator to collect prompt gamma radiation in coincidence with recoils implanted in a silicon strip detector located at the focal plane of RITU. Using a selective recoil decay tagging technique it has been possible to unambiguously assign gamma -ray transitions to Os-167 and Os-168 through the characteristic a radioactivity of these nuclides. The high-spin structure of the bands is discussed in terms of quasiparticle configurations within the framework of the cranked shell model. The role of shape coexistence in Os-168 is examined with phenomenological three-band mixing calculations.
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| 13. |
- Lieder, R. M., et al.
(författare)
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From highly to superdeformed shapes : study of Gd-143
- 2000
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 671:04-jan, s. 52-70
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Tidskriftsartikel (refereegranskat)abstract
- A superdeformed band has been discovered in Gd-143 consisting Of 15 transitions. It does not show the band crossing observed in the neighbouring heavier Gd isotopes and it is degenerate with the superdeformed band in Eu-143. In contrast to other degenerate bands at superdeformed shape, the configurations of the bands are quite different here. They result from the exchange of a nu 6(4) with a pi[404]9/2 configuration. In addition, a collective band has been observed which adopts a well-deformed triaxial shape at high spins according to calculations. The transition from highly to superdeformed shapes proceeds via triaxial shapes.
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| 14. |
- Lieder, R. M., et al.
(författare)
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The TMR network project Development of gamma-ray tracking detectors
- 2001
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Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 682, s. 279C-285C
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Tidskriftsartikel (refereegranskat)abstract
- The next generation of 4 pi arrays for high-precision gamma -ray spectroscopy will involve gamma -ray tracking detectors. They consist of high-fold segmented Ge detectors and a front-end electronics, based on new digital signal processing techniques, which allows to extract energy, timing and spatial information for a gamma -ray by pulse shape analysis of the Ge detector signals. Utilizing the information on the positions of the interaction points and the energies released at each point the tracks of the gamma -rays in a Ge shell can be reconstructed in three dimensions.
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| 15. |
- Perez, G. E., et al.
(författare)
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Structure of high-spin states in Pd-100
- 2001
-
Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 686, s. 41-63
-
Tidskriftsartikel (refereegranskat)abstract
- High-spin states of the neutron deficient (100)pd nucleus have been investigated via the Cr-50(Ni-58, 4p alpha) and Zn-70(S-36,6n) heavy-ion induced reactions. For the detection of evaporated particles and gamma rays the NORDBALL array equipped with ancillary detectors and the EUROGAM II detector system were utilized. By the use of in-beam spectroscopic methods 89 transitions belonging to (100)pd have been observed, 49 of which were identified for the first time. The level scheme has been extended up to E-X approximate to 16 MeV excitation energy and I approximate to 25h. The experimental results were compared with the predictions of cranked shell model calculations. Maximal spin alignments were found in the (pig(9/2))(12+)(-4) (vd(5/2),g(7/2)(3)h(11/2))(13-) and (pig(9/2)(-3)p(1/2))(11-)(vd(5/2)g(7/2)(3)h(11/2))(13-) configurations. Possible existence of octupole correlations is discussed on the basis of 6 (E 1)lB(E2) values deduced for the decays of high-spin levels in the yrast negative-parity band.
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| 16. |
- Satula, W., et al.
(författare)
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A number projected model with generalized pairing interaction
- 2000
-
Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 676, s. 120-142
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Tidskriftsartikel (refereegranskat)abstract
- A mean-held model with a generalized pairing interaction that accounts for neutron-proton pairing is presented. Both the BCS as well as number-projected solutions of the model are presented. For the latter case the Lipkin-Nogami projection technique was extended to encompass the case of nonseparable proton-neutron systems. The influence of the projection on various pairing phases is discussed. In particular, it is shown that number-projection allows For mixing of different pairing phases but, simultanously, acts destructively on the proton-neutron correlations, The basic implications of proton-neutron pairing correlations on nuclear masses are discussed. It is shown that these correlations may provide a natural microscopic explanation of the Wigner energy lacking in mean-field models. A possible phase transition from isovector to isoscalar pairing condensate at high angular momenta is also discussed. In particular predictions for the dynamical moments of inertia for the superdeformed band in Ru-88 are given.
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| 17. |
- Singh, A. K., et al.
(författare)
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Detailed study of magnetic rotation in (196)pb
- 2002
-
Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 707:02-jan, s. 3-31
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Pb-196 have been populated in two different heavy-ion-induced reactions using thin and Au-backed targets, respectively. Gamma-ray coincidences were measured using the EUROBALL spectrometer array. Five new magnetic-rotational bands have been found. The previously known four bands have been extended and some of their levels have been reordered. With one exception, all the bands have been connected to lower-lying states and excitation energies, spins and parities have been determined. From the systematic properties of the bands and from comparison to tilted-axis cranking calculations, arguments for configuration assignments to the bands are derived. It is suggested that the bands are based on proton 11(-) and 8(+) particle states coupled to various neutron-hole excitations.
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| 18. |
- Spolaore, P., et al.
(författare)
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Identification and study of the very neutron deficient nuclide I-111 : search for octupole correlations in the region of N approximate to Z approximate to 56
- 2001
-
Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 682, s. 387C-393C
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in the neutron-deficient nuclide I-111 have been populated with the fusion reaction Ni-58 + Ni-58 at a beam energy of 210 MeV, in an experiment performed at the Tandem Accelerator of the Laboratori Nazionali di Legnaro. The gamma spectrometer GASP was used in time coincidence with the ISIS Si-ball and the CAMEL recoil mass spectrometer for the positive identification of the nuclide. Gamma transitions and structure details previously attributed to I-111 by Other authors are only partially confirmed. The obtained level scheme includes new rotational bands and a new low lying structure which suggests the presence of octupole correlations at predicted rotational frequency values.
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| 19. |
- Xu, F. R., et al.
(författare)
-
Quadrupole pairing interaction and signature inversion
- 2000
-
Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 669:02-jan, s. 119-134
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Tidskriftsartikel (refereegranskat)abstract
- The signature inversion in the pi h(11/2) x vh(11/2) rotational bands of the odd-odd Cs and La isotopes and the pi h(11/2) x vi(13/2) bands of the odd-odd Tb, Ho and Tm nuclei is investigated using pairing and deformation self-consistent mean-field calculations, The model can rather satisfactorily account for the anomalous signature splitting provided that spin assignments in some of the bands are revised. Our calculations show that signature inversion can appear already at axially symmetric shapes. It is found that this is due to the contribution of the (lambda mu) = (22) component of the quadrupole-pairing interaction to the mean-field potential.
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| 20. |
- Aad, G., et al.
(författare)
-
The ATLAS Collaboration
- 2009
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 830:1-4, s. 925c-940c
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Tidskriftsartikel (refereegranskat)
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| 21. |
- Bergenwall, B., et al.
(författare)
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Neutron-induced light charged particle production in carbon at 96 MeV
- 2005
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 747:2-4, s. 152-181
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Tidskriftsartikel (refereegranskat)abstract
- Differential cross sections of charged particle production, i.e., p, d, t, 3He-ions and α-particles, in 96 MeV neutron-carbon interactions have been measured at laboratory angles in the range 20° to 160° in steps of 20°. The experimental techniques are described as well as the procedures for acquisition, analysis, reduction and correction of the data. Results including double differential, energy-differential, angle-differential and total particle production cross sections are reported and constitute the first data set with five ejectiles at such a high neutron energy. Thanks to the low-energy thresholds, 50% of the production cross section of α-particles, and 85% of the production cross sections of protons and deuterons, could be measured. For α-particles, the measured fraction is much higher than what has been achieved earlier at lower energies. The results on the hydrogen isotopes agree fairly well with a previous measurement at 95 MeV and with recent GNASH calculations. For the helium isotopes, however, there are important discrepancies in spectral shape and magnitude between the new results and the model calculations.
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| 22. |
- Birgersson, Evert, et al.
(författare)
-
Light fission-fragment mass distribution from the reaction 251Cf(nth, f)
- 2007
-
Ingår i: Nuclear Physics A. - Amsterdam : Elsevier. - 0375-9474 .- 1873-1554. ; 791:1-2, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- For mass numbers A = 80 to 124 the recoil mass spectrometer LOHENGRIN of the Institute Laue-Langevin in Grenoble was used to measure with high resolution the light fission-fragment mass yields and kinetic energy distributions from thermal-neutron induced fission of 252Cf* for the first time, using 251Cf as target material. The obtained mean light fragment mass AL = (107 ± 2) and the corresponding mean kinetic energy Ek,L = (103±2) MeV are within the expected trend. Emission yields around A = 115 are enhanced and the corresponding mean kinetic energy is higher compared to spontaneous fission of 252Cf. This could be explained by the existence of an additional super-deformed fission mode.
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| 23. |
- Birgersson, Evert, et al.
(författare)
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Properties of the reaction 238U(n, f) at the vibrational resonances
- 2009
-
Ingår i: Nuclear Physics A. - Amsterdam : Elsevier. - 0375-9474 .- 1873-1554. ; 817:1-4, s. 1-34
-
Tidskriftsartikel (refereegranskat)abstract
- Recent fission cross-section calculations for the reaction 238U(n, f ), based on an extended statistical model, predict a significant change of fission fragment properties, such as the mean mass by A = 1.5 and a notable increase in total kinetic energy in the region of the vibrational resonance at an incident neutron energy En = 0.9 MeV. This model includes individual fission cross-sections by the asymmetric standard 1 (S1) and standard 2 (S2) as well as the symmetric super-long (SL) mode. In order to verify the model predictions, a dedicated experiment on 238U has been carried out to measure fission-fragment mass yield distributions for incident neutron energies from En = 2.0 MeV down to 0.9 MeV, where the fission characteristics at the vibrational resonance at En = 0.9 MeV were investigated for the first time. The previously reported distinct structure in the angular anisotropy around En = 1.2 and 1.6 MeV wasobserved at En = 0.9 MeV as well. The predicted large changes in fission fragment mass yield and total kinetic energy could not be confirmed. In the resonance the mean total kinetic energy is only about 0.5 MeV higher than at En = 1.8 MeV. At the same time, a slight decrease of the mean heavy fragment mass was observed, probably indicating a slightly increased contribution of the S1 fission mode.
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| 24. |
- Blaschke, David, et al.
(författare)
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Diquark condensation effects on hot quark star configurations
- 2004
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 736:1-2, s. 203-219
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Tidskriftsartikel (refereegranskat)abstract
- The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the formfactors of the interaction on the phase diagram of quark matter. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state under the condition of β-equilibrium and charge neutrality. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2˜1053 erg. We find that this energy could not serve as an engine for explosive phenomena since the phase transition is not first order. Contrary to naive expectations the mass defect increases when for a given temperature we neglect the possibility of diquark condensation.
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| 25. |
- Boutami, R., et al.
(författare)
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Nuclear structure of Ac-231
- 2008
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 811:3-4, s. 244-275
-
Tidskriftsartikel (refereegranskat)abstract
- The low-energy structure of Ac-231 has been investigated by means of gamma ray spectroscopy following the beta(-) decay of Ra-231. Multipolarities of 28 transitions have been established by measuring conversion electrons with a MINI-ORANGE electron spectrometer. The decay scheme of Ra-231 -> Ac-231 has been constructed for the first time. The Advanced Time Delayed beta gamma gamma(t) method has been used to measure the half-lives of five levels. The moderately fast B(EI) transition rates derived suggest that the octupole effects., albeit weak, are still present in this exotic nucleus.
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| 26. |
- Costantini, H., et al.
(författare)
-
Recent results of the 14N(p,γ)15O measurement at LUNA
- 2005
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 758:1-4 SPEC. ISS., s. 383C-386C
-
Tidskriftsartikel (refereegranskat)abstract
- The 14N(p, γ)15O reaction has been investigated by LUNA at the National Laboratory of Gran Sasso (LNGS) using two different techniques. The first study has been performed using a solid target and detecting the γ-rays coming from the single transitions with a HPGe detector in very close geometry to the target. In a second phase a windowless gas target sorrounded by a nearly 4π BGO summing crystal has been used and the total S-factor has been measured down to Eb = 80 keV. © 2005 Elsevier B.V. All rights reserved.
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| 27. |
- Dombey, S., et al.
(författare)
-
QCD evolution of jets in the quark-gluon plasma
- 2008
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 808, s. 178-191
-
Tidskriftsartikel (refereegranskat)abstract
- The quark-gluon plasma (QGP) can be explored in relativistic heavy ion collisions by the jet quenching signature, i.e. by the energy loss of a high energy quark or gluon traversing the plasma. We introduce a novel QCD evolution formalism in the leading logarithm approximation, where normal parton radiation is interleaved with scattering on the plasma gluons occuring at a similar time scale. The idea is elaborated in two approaches. One extends the DGLAP evolution equations for fragmentation functions to include scatterings in the medium, which facilitates numerical solutions for comparison with data and provides a basis for a Monte Carlo implementation. The other approach is more general by including also the transverse momentum dependence of the jet evolution, which allows a separation of the scales also for the scattering term and provides a basis for analytical investigations. The two approaches are shown to be related and give the same characteristic softening of the jet depending on the temperature of the plasma. A substantial effect is found at the RHIC energy and is further enhanced at LHC. Systematic studies of data on the energy loss could, therefore, demonstrate the existence of the QGP and probe its properties.
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| 28. |
- Dussel, G. G., et al.
(författare)
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One- and two-quasiparticle states in the complex energy plane
- 2007
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 789, s. 182-200
-
Tidskriftsartikel (refereegranskat)abstract
- One- and two-quasi particle states are studied in the complex energy plane. It is found that the pairing interaction does not change the character of the complex state. If a normal state is a physically meaningful resonance, then it will remain as such throughout the shell and if it is unphysical it will also remain as such throughout the shell. An important consequence of this is that it justifies the use of bound representations to evaluate many-body systems within the shell-model in cases where the single-particle states are narrow resonances. The character of two-quasiparticle states may oscillate between meaningful resonances and unphysical complex excitations as the number of particles increases.
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| 29. |
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| 30. |
- Froelich, Piotr, et al.
(författare)
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Hydrogen - Antihydrogen Collisions
- 2001
-
Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 692:1-2, s. 182c-183c
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Tidskriftsartikel (refereegranskat)
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| 31. |
- Golubev, Pavel, et al.
(författare)
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Pion Emission in H-2,C-12,Al-27(gamma,pi+) Reactions at Threshold
- 2008
-
Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 806:1-4, s. 216-229
-
Tidskriftsartikel (refereegranskat)abstract
- The very first data from MAX-lab in Lund, Sweden on pion photoproduction at threshold energies are presented. The decrease of the total π+ yield in γ+12C, 27Al reactions below 200 MeV as well as the dσ/dΩ cross-section data essentially follow the predictions of an intranuclear-cascade model with an attractive potential for the pion–nucleus interaction. However, View the MathML source, cross-section data at 176 MeV show deviations which call for refinements of the model and possibly also for the inclusion of coherent pion-production mechanisms.
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| 32. |
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| 33. |
- Huber, S. J., et al.
(författare)
-
Baryogenesis in the MSSM, nMSSM and NMSSM
- 2007
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 785:1-2, s. 206C-209C
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Tidskriftsartikel (refereegranskat)
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| 34. |
- Keleta, S, et al.
(författare)
-
Exclusive measurement of two-pion production in the dd -> He-4 pi pi reaction
- 2009
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 825:1-2, s. 71-90
-
Tidskriftsartikel (refereegranskat)abstract
- The results from the first kinematically complete measurement of the dd -> He-4 pi pi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pi pi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV. with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pi pi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, Our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN -> d pi sub-processes. (C) 2009 Elsevier B.V. All rights reserved.
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| 35. |
- Oberstedt, Stephan, et al.
(författare)
-
Light charged particle emission in the reaction 251Cf(nth, f)
- 2005
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 761:3-4, s. 173-189
-
Tidskriftsartikel (refereegranskat)abstract
- High resolution measurements of light charged particles (LCP) emitted in thermal neutron-induced fission of 252Cf ∗ (E=6.2 MeV) have been performed with the recoil mass-separator LOHENGRIN. For this compound nuclear system emission yields of LCPs, their mean kinetic energies and widths have been obtained for 8 isotopes with nuclear charges Z⩾2. For 13 further isotopes the emission yields were estimated on the basis of systematics on their kinetic energy distributions. 34Al and 36Si emission has been observed for the first time in thermal neutron-induced fission.
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| 36. |
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| 37. |
- Qi, Chong, 1983-, et al.
(författare)
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Shell-model study of spectroscopies and isospin structures in odd-odd N=Z nuclei employing realistic NN interaction
- 2008
-
Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 800:1-4, s. 47-62
-
Tidskriftsartikel (refereegranskat)abstract
- The structures of odd-odd N = Z nuclei in the lower fp shell have been investigated with a new microscopic interaction. The interaction is derived from a high-precision charge-dependent Bonn nucleon-nucleon potential using the folded-diagram renormalization method. Reasonable agreements with experimental data have been obtained. Particularly, the relative positions of T = 0 and T = I bands are well reproduced. As examples, the spectroscopies and isospin structures of (46)V and (50)Mn have been discussed in details, with the useful predictions of level structures including electromagnetic properties. Some unique features in these nuclei can be used to increase the understanding of the effective interaction theory. Our calculations show that the realistic effective interaction which is directly related to nucleon-nucleon scattering can give the reasonable descriptions of the collective properties of nuclear many-body system without any empirical modification.
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| 38. |
- Schönning, Karin
(författare)
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The production of omega-mesons in pd -> He-3 omega near the kinematic threshold
- 2007
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 790, s. 319C-322C
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Tidskriftsartikel (refereegranskat)abstract
- The production of omega mesons in pd -> He-3 omega has been studied with the WASA detector at two energies near the kinematic threshold, corresponding to p(omega)(*) = 280 MeV/c and p(omega)(*) = 144 MeV/c. For p(omega)(*) = 280 MeV/c, the differential cross section as a function of cos(theta(*)(omega)) has been extracted. The result indicates contributions from higher partial waves.
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| 39. |
- Sohler, D, et al.
(författare)
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Band-terminating states in Ag-101
- 2004
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 733:1-2, s. 37-52
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Tidskriftsartikel (refereegranskat)abstract
- Excited states of the neutron deficient Ag-101 nucleus have been investigated via the Cr-50(Ni-58, 3rho1alpha) heavy-ion induced reaction at 261 meV by use of in-beam spectroscopic methods. On the basis of the measured gammagamma-cincidence relations and angular distribution ratios high-spin bands have been extended up to I-pi = 35/2(+), 45/2((-)) and (49/2(-)). The negative parity states at the highest energy have been interpreted as terminating non-collective oblate states in the framework of the Nilsson-Strutinsky cranking formalism.
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| 40. |
- Sohler, D, et al.
(författare)
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Maximally Aligned States in the Proton Drip Line Nucleus 106Sb
- 2005
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 753:3-4, s. 251-262
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Sb-106 have been investigated in the Fe-54(Ni-58, 1α 1p1n) reaction by in-beam γ-spectroscopic methods using the EUROBALL detector array equipped with charged particle and neutron detectors. On the basis of measured γγ-coincidence relations, angular distributions, and linear polarization ratios a significantly extended level scheme has been constructed up to spin and parity I-π = (19(-)) and E-x ∼ 6.5 MeV. The experimental results are interpreted within the framework of the gdsh shell model using a realistic effective nucleon-nucleon interaction. Candidates for states with fully aligned angular momenta in the π(d(5/2), g(7/2))(1) v (d(5/2), g(7/2))(5) valence space are identified at 4338 and 5203 keV, as well as in the π(d(5/2), g(7/2))(1) V(d(5/2), g(7/2))(4)h(11/2)(1) space at 6087, 6573 and 6783 keV.
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| 41. |
- Stanoiu, M., et al.
(författare)
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Study of neutron rich carbon and oxygen nuclei up to drip line
- 2004
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 746, s. 135C-139C
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Tidskriftsartikel (refereegranskat)abstract
- In-beam gamma-spectroscopy using fragmentation reactions of radioactive beams have been performed in order to study the structure of excited states in neutron rich oxygen and carbon isotopes. For the produced fragments, gamma-ray energies, intensities and gamma-gamma coincidences have been measured. The experiment was performed at GANIL. New gamma-lines have been identified and placed in level schemes for C17-20. The non observation of any gamma-ray in O-23,O-24 suggests that their first excited states lie above the neutron threshold. These results are discussed in the framework of shell model calculations.
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| 42. |
- Tovesson, Fredrik, et al.
(författare)
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233Pa(n, f) cross section up to En=8.5 MeV
- 2004
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 733:1-2, s. 3-19
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Tidskriftsartikel (refereegranskat)abstract
- The energy dependence of the neutron-induced fission cross section of 233Pa has been measured directly for the first time from the fission threshold up to En=8.5 MeV. This reaction plays an important role in the thorium-uranium fuel cycle, and is thus of interest for the design and modeling of advanced reactor and transmutation facilities. The existing information in the ENDF/B-VI and JENDL-3.3 evaluated nuclear data files differ by a factor of two for the 233Pa(n, f) cross section values and show different fission threshold energies. Our new experimental data give lower cross section values than both evaluations and resolves the question about the threshold energy. In addition to the experimental investigation, also a new theoretical calculation of the reaction cross section has been performed with the statistical model code STATIS, showing a good agreement with the experimental data.
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| 43. |
- Vladuca, G., et al.
(författare)
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Calculation of the neutron-induced fission cross section of 233Pa up to 20 MeV
- 2004
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 740:1-2, s. 3-19
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Tidskriftsartikel (refereegranskat)abstract
- Since very recently, direct measurements of the 233Pa(n,f) cross-section are available in the energy range from 1.0 to 8.5 MeV. This has stimulated a new, self-consistent, neutroncross-section evaluation for the n+233Pa system, in the incident neutron energy range 0.01–20MeV. Since higher fission chances are involved also the lighter Pa-isotopes had to be re-evaluated in a consistent manner. The results are quite different compared to earlier evaluation attempts. Since 233Pa is a key isotope in the thorium based fuel cycle the quality of its reaction cross-sections is important for the modeling of future advanced fuel and reactor concepts. The present status of the evaluated libraries is that they differ by a factor of two in the absolute fissioncross-section and also in the threshold energy value.
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| 44. |
- Watanabe, H., et al.
(författare)
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Application of the high-spin isomer beams to the secondary fusion reaction and the measurement of g-factor
- 2004
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 746, s. 540C-543C
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Tidskriftsartikel (refereegranskat)abstract
- A technique for providing high-spin isomers as probes of the fusion reaction and the measurement of g-factor has been worked out at RIKEN. In the study of the fusion reaction C-12(Sm-145m,xn)Er157-x, the gamma rays emitted from the fusion-evaporation residue Er-154 have been successfully observed. The nuclear g-factor of the T-1/2 = 28 ns high-spin isomer in Dy-149 has been measured with the gamma-ray TDPAD method.
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| 45. |
- Axelsson, A, et al.
(författare)
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A critical appraisal of the rediagonalization method for construction of diabatic levels
- 2002
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Ingår i: Nuclear Physics, Section A. - 0375-9474. ; 708:3-4, s. 226-244
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Tidskriftsartikel (refereegranskat)abstract
- The possibilities and limitations of the rediagonalization method for detection and removal of virtual interactions at bandcrossings are explored in the framework of the cranked Nilsson-Strutinsky shell model. Improvements of the method are suggested.
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| 46. |
- Axelsson, A, et al.
(författare)
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An investigation of pairing correlations in diabatic configurations at high spin and large deformation: applications to the description of SD bands in Eu-143
- 2002
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Ingår i: Nuclear Physics, Section A. - 0375-9474. ; 708:3-4, s. 245-276
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Tidskriftsartikel (refereegranskat)abstract
- The HFB cranked shell model is applied in an investigation of the selfconsistent pairing properties of the superdeformed (SD) bands in Eu-143. Results from a fully pairing and deformation selfconsistent mesh calculation of the properties of the most intense SD band in 143Eu are presented, as well as pairing selfconsistent calculations done at a fixed deformation close to the SD minimum for an excited SD configuration. The calculations are compared to unpaired calculations and to published experimental data. Fully diabatic configurations are studied and total energy surfaces are constructed for fixed values of the angular momentum. Other issues addressed include the development of the particle number distribution in the HFB wave function up to very high frequency, the consequences of using a fixed Fermi energy in high-spin calculations and the effects of the number of excited quasiparticles on the pairing properties of the superdeformed nucleus. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 47. |
- Axelsson, L., et al.
(författare)
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Deriving the angular variation of p(parallel to)-distributions for halo neutrons with robust statistics
- 2001
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Ingår i: Nuclear Physics A. - 0375-9474. ; 679:3-4, s. 215-230
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Tidskriftsartikel (refereegranskat)abstract
- The longitudinal neutron momentum distribution from core breakup of Li-11 and Be-11 have been measured at 29.9 MeV/u and 38.5 MeV/u, respectively. Separate measurements on Li-9 and Be-10 allowed extraction of the halo neutron distribution. The shapes of the distributions are analyzed using robust and descriptive statistics, For both isotopes the shape is changing with angle. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 48. |
- Bennett, J. R. J., et al.
(författare)
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Release studies of a thin foil tantalum target for the production of short-lived radioactive nuclei
- 2002
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Ingår i: Nuclear Physics A. - 0375-9474. ; 701, s. 327C-333C
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Konferensbidrag (refereegranskat)abstract
- Measurements have been made at ISOLDE, of the release curves and yields of radioactive beams of lithium, sodium and beryllium from a target constructed from 2 pm thick foils. The release curves have been analysed by fitting to a mathematical model to determine the coefficients of diffusion of the particles in the foils and effusion through the target and ionizer at several temperatures. Through a better understanding of the rate of transport of the particles, it is possible to design targets and ionizers with improved yields. This is most important for the rare, short-lived isotopes in which there is considerable interest for physics experiments. This target has demonstrated large increases in the yields of Li-11 and Be-12, in agreement with the predictions of the model. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 49. |
- Bergmann, U. C., et al.
(författare)
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Beta-decay properties of the neutron-rich Kr94-99 and Xe142-147 isotopes
- 2003
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Ingår i: Nuclear Physics A. - 0375-9474. ; 714:1-2, s. 21-43
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Tidskriftsartikel (refereegranskat)abstract
- Beta-decay half-lives and delayed-neutron emission probabilities of the neutron-rich noble-gas isotopes Kr94-99 and Xe142-147 have been measured at the PSB-ISOLDE facility at CERN. The results are compared to QRPA shell-model predictions and are used in dynamic calculations of r-process abundances of Kr and Xe isotopes. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 50. |
- Bergmann, U. C., et al.
(författare)
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On the beta-decay of C-9
- 2001
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Ingår i: Nuclear Physics A. - 0375-9474. ; 692:3-4, s. 427-450
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Tidskriftsartikel (refereegranskat)abstract
- In beta -decay experiments on C-9 at CERN/ISOLDE the beta -strength was determined to the ground state, the 12.2 MeV excited state and the Isobaric Analog State (IAS) at 14.655 MeV in B-9. A large beta -strength asymmetry is deduced for the mirror transitions of C-9 and Li-9 to states around 12 MeV excitation energy. A satisfactory description of the three-body decay from a narrow energy region around the 12.2 MeV resonance is obtained within a sequential model involving the ground and first-excited states of Li-5 and Be-8. From the study of angular correlations the spin of the 12.2 MeV state is determined as 5/2(-). For the first time the population of the IAS is observed in beta -decay and new information on the decay of this state is obtained. The advantages of a closely packed. highly segmented detector setup are demonstrated. (C) 2001 Elsevier Science B.V. All rights reserved.
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