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  • Adlarson, Patrik, et al. (författare)
  • Cross section ratio and angular distributions of the reaction p + d -> He-3 + eta at 48.8MeV and 59.8MeV excess energy
  • 2014
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 50:6, s. 100
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present new data for angular distributions and on the cross section ratio of the p+d -&gt; He-3+eta reaction at excess energies of Q - 48.8MeV and Q - 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum Julich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.</p>
  • Al-Adili, Ali, et al. (författare)
  • Extraction of angular momenta from isomeric yield ratios Employing TALYS to de-excite primary fission fragments
  • 2019
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 55:4
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The generation of angular momentum in fission is difficult to model, in particular at higher excitation energies where data are scarce. Isomeric yield ratios (IYR) play an important role in deducing angular momentum properties of fission fragments (FF), albeit this requires some assumptions and simplifications. To estimate FF angular momentum, fission codes can be used to calculate IYRs and compare them to experimental data. Such measurements have systematically been performed at the IGISOL facility using novel experimental techniques. In conjunction, a new method has been developed to infer the angular momentum of the primary FF using the nuclear reaction code TALYS. In this work, we evaluate this new method by comparing our TALYS calculations with values found in the literature and with results from the GEF fission code, for a few well-studied reactions. The overall results show a consistent performance of TALYS and GEF, as well as of many reported literature values. However, some deviations were found, possibly pinpointing the need to re-examine some of the reported literature values. A sensitivity analysis was also performed, in which the role of excitation energy, neutron emission, discrete level structure and level density models were studied. Finally, the role of multiple chance fission, of relevance for the reactions studied at IGISOL, is discussed. Some literature data for this reaction were also re-analyzed using TALYS, revealing significant differences.</p>
  • Al-Adili, Ali, et al. (författare)
  • Simulations of the fission-product stopping efficiency in IGISOL
  • 2015
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 51:59, s. 1-7
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>At the Jyväskylä Ion Guide Isotope Separator On-Line (IGISOL) facility, independent fission yields are measured employing the Penning-trap technique. Fission products are produced, <em>e.g.</em> by impinging protons on a uranium target, and are stopped in a gas-filled chamber. The products are collected by a flow of He gas and guided through a mass separator to a Penning trap, where their masses are identified. This work investigates how fission-product properties, such as mass and energy, affect the ion stopping efficiency in the gas cell. The study was performed using the Geant4 toolkit and the SRIM code. The main results show a nearly mass-independent ion stopping with regard to the wide spread of ion masses and energies, with a proper choice of uranium target thickness. Although small variations were observed, in the order of 5%, the results are within the systematic uncertainties of the simulations. To optimize the stopping efficiency while reducing the systematic errors, different experimental parameters were varied; for instance material thicknesses and He gas pressure. Different parameters influence the mass dependence and could alter the mass dependencies in the ion stopping efficiency.</p>
  • Andreyev, A. N., et al. (författare)
  • New microsecond isomers in Bi-189,Bi-190
  • 2001
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 10:2, s. 129-133
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>New microsecond isomers in the neutron-deficient isotopes Bi-189g,Bi-190 have been identified after in-flight separation by the velocity filter SHIP. The evaporation residues were identified on the basis of delayed recoil-gamma /X-ray, recoil-gamma /X-ray-alpha and excitation function measurements. The systematics of the [pi 1i(13/2)]13/2(+) excited states in the odd-mass Bi nuclei is discussed.</p>
  • Assié, M., et al. (författare)
  • Neutron correlations in <sup>6</sup>He viewed through nuclear break-up
  • 2009
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 42:3, s. 441-446
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The nuclear break-up of He-6 on a Pb-208 target was studied at 20 A MeV using a secondary beam of He-6 produced by the SPIRAL facility at GANIL. alpha-particles were detected in coincidence with two neutrons with a large angular coverage and the reaction mechanism was identified. From the distribution of the relative angles between the two neutrons the correlation function was extracted. It shows a strong correlation at small relative angles attributed to the contribution of the di-neutron configuration of He-6.</p>
  • Assie, M., et al. (författare)
  • The Giant Pairing Vibration in heavy nuclei Present status and future studies
  • 2019
  • Ingår i: European Physical Journal A. - SPRINGER. - 1434-6001 .- 1434-601X. ; 55:12
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The Giant Pairing Vibration, a two-nucleon collective mode originating from the second shell above the Fermi surface, has long been predicted and expected to be strongly populated in two-nucleon transfer reactions with cross sections similar to those of the low-lying Pairing Vibration. Recent experiments have provided evidence for this mode in C-14,C- 15 but, despite sensitive studies, it has not been definitively identified in Sn or Pb nuclei where pairing correlations are known to play a crucial role near their ground states. In this paper we review the basic theoretical concepts of this "elusive" state and the status of experimental searches in heavy nuclei. We discuss the hindrance effects due to Q-value mismatch and the use of weakly-bound projectiles as a way to overcome the limitations of the (p,t) reactions. We also discuss the role of the continuum and conclude with some possible future developments.</p>
  • Axelsson, A, et al. (författare)
  • Excited superdeformed band in Eu-143
  • 1999
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 6:2, s. 175-183
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>A new superdeformed band has been discovered in a EUROBALL experiment and assigned to Eu-143. It has a maximum intensity of 35% of the Eu-143 yrast superdeformed band and the transition energies of the two bands are very similar. Based on comparison with cranked shell model calculations the new band is tentatively assigned the high-N intruder configuration pi 6(2)nu 7(0) and the parity and signature quantum numbers (pi, alpha) = (-1, +1/2). In addition to the already known high-energy transition at 3361 keV another discrete line at 2715 keV was found to be in coincidence with the yrast superdeformed band. However, it was not possible to connect the decay out of either of the superdeformed bands to, known normally deformed states.</p>
  • Barucca, G., et al. (författare)
  • Precision resonance energy scans with the PANDA experiment at FAIR : Sensitivity study for width and line shape measurements of the X(3872)
  • 2019
  • Ingår i: European Physical Journal A. - Springer. - 1434-6001 .- 1434-601X. ; 55:3
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>.This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from JPC=1--.</p>
  • Bemmerer, D., et al. (författare)
  • Feasibility of low-energy radiative-capture experiments at the LUNA underground accelerator facility
  • 2005
  • Ingår i: European Physical Journal A. - 1434-6001 .- 1434-601X. ; 24:2, s. 313-319
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The LUNA (Laboratory Underground for Nuclear Astrophysics) facility has been designed to study nuclear reactions of astrophysical interest. It is located deep underground in the Gran Sasso National Laboratory, Italy. Two electrostatic accelerators, with 50 and 400 kV maximum voltage, in combination with solid and gas target setups allowed to measure the total cross-sections of the radiative-capture reactions 2H2H(p, γ) 3He3Heand 14N14N(p, γ) 15O15Owithin their relevant Gamow peaks. We report on the gamma background in the Gran Sasso laboratory measured by germanium and bismuth germanate detectors, with and without an incident proton beam. A method to localize the sources of beam-induced background using the Doppler shift of emitted gamma rays is presented. The feasibility of radiative-capture studies at energies of astrophysical interest is discussed for several experimental scenarios. © Società Italiana di Fisica/Springer-Verlag 2005.</p>
  • Bergmann, U. C., et al. (författare)
  • Analysis of decay data from neutron-rich nuclei
  • 2001
  • Ingår i: European Physical Journal A. - 1434-601X .- 1434-6001. ; 11:3, s. 279-284
  • Tidskriftsartikel (refereegranskat)abstract
    • The beta -decays of the neutron-rich nuclei Be-12 and Ne-29 have been studied. The statistical correlations between the almost identical half-lives of Be-12 and its daughter B-12 are analysed for a large sample of Be-12 decay data. Stringent mutual bounds are obtained on the parameter set, leading to a precise determination of the Be-12 half-life of 21.50 +/- 0.04 ms. From a simultaneous detection of beta -particles and neutrons from the decay of Ne-29 the neutron emission probability, P-n, is determined to 17 +/- 5%. No indication of two-neutron emission is seen from this nucleus. An upper limit of 2.2% (90% confidence level) is established for P-2n.
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