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Sökning: WFRF:(Jonsell Svante)

  • Resultat 61-70 av 116
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61.
  • Jonsell, Svante, et al. (författare)
  • Fine Structure in Cold Collisions of Spin-Polarized H(2s) Atoms
  • 2004
  • Ingår i: Physica scripta. T. - 0281-1847. ; T110, s. 299-301, s. 299-301
  • Tidskriftsartikel (refereegranskat)abstract
    • We have calculated cross sections and rate coefficients for elastic scattering, ionization, and double excitation transfer in collision of two hydrogen atoms in the 2s state. We find that for collision energies between 5 × 10-10 a.u. and 10-6 a.u. elastic scattering has the largest cross section. For temperatures below 0.02 K ionization is the dominant loss process, while for higher temperatures double excitation transfer dominates. Our results for the total loss rate are found to be within a factor 2 or 3 of the error bars of recent measurements.  
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62.
  • Jonsell, Svante, et al. (författare)
  • Formation of antihydrogen beams from positron-antiproton interactions
  • 2019
  • Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21
  • Tidskriftsartikel (refereegranskat)abstract
    • The formation of a beam of antihydrogen atoms when antiprotons pass through cold, dense positron plasmas is simulated for various plasma properties and antiproton injection energies. There are marked dependences of the fraction of injected antiprotons which are emitted as antihydrogen in a beam-like configuration upon the temperature of the positrons, and upon the antiproton kinetic energy. Yields as high as 13% are found at the lowest positron temperatures simulated here (5K) and at antiproton kinetic energies below about 0.1 eV. By 1 eV the best yields are as low as 10(-3), falling by about two orders of magnitude with an increase of the positron temperature to 50 K. Example distributions for the antihydrogen angular emission, binding energy and kinetic energy are presented and discussed. Comparison is made with experimental information, where possible.
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63.
  • Jonsell, Svante, et al. (författare)
  • Helium-antihydrogen scattering at low energies
  • 2012
  • Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 035013-
  • Tidskriftsartikel (refereegranskat)abstract
    • We calculate cross sections for helium-antihydrogen scattering for energies up to 0.01 atomic unit. Our calculation includes elastic scattering, direct antiproton-alpha particle annihilation and rearrangement into He(+)p(-) and ground-state positronium. Elastic scattering is calculated within the Born-Oppenheimer approximation using the potential calculated by Strasburger et al (2005 J. Phys. B: At. Mol. Opt. Phys. 38 3091). Matrix elements for rearrangement are calculated using the T-matrix in the distorted wave approximation, with the initial state represented by Hylleraas-type functions. The strong force, leading to direct annihilation, was included as a short-range boundary condition in terms of the strong-force scattering length.
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64.
  • Jonsell, Svante, et al. (författare)
  • Hydrogen : Antihydrogen Scattering in the Born-Oppenheimer Approximation
  • 2004
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:6, s. 1195-
  • Tidskriftsartikel (refereegranskat)abstract
    • We calculate the low-energy scattering between hydrogen and antihydrogen atoms in their ground states using the Born–Oppenheimer approximation. Improved results for rearrangement, direct annihilation and elastic scattering are presented. The elastic cross section agrees well with other calculations. For the rearrangement process we confirm a recent result (Armour E A G and Chamberlain C W 2002 J. Phys. B: At. Mol. Opt. Phys. 35 L489) that rearrangement to the N = 23 state of protonium has a larger cross section than rearrangement to the N = 24 state. For both rearrangement cross sections our results are smaller than those obtained by Armour and Chamberlain. The direct annihilation, and its influence on elastic scattering, is calculated using the scattering length for the strong force between the proton and antiproton. This approach gives strong-force effects qualitatively similar, but smaller than those obtained in another recent work (Voronin A Yu and Carbonell J 2001 Nucl. Phys. A 689 529c).
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65.
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66.
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67.
  • Jonsell, Svante, et al. (författare)
  • Including the strong nuclear force in antihydrogen-scattering calculations
  • 2005
  • Ingår i: Canadian journal of physics (Print). - : Canadian Science Publishing. - 0008-4204 .- 1208-6045. ; 83:4, s. 435-445
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate two methods to include the strong nuclear force in hydrogen-antihydrogen scattering calculations. First, we construct a model optical potential with parameters determined by the measured shift and width of the protonium ground state. Although this potential is a very crude model for the strong nuclear force, its parameters may be adjusted to reproduce both bound states and low-energy annihilation cross sections to within the experimental accuracy. It is then shown that this potential may be reduced to a short-distance boundary condition in terms of the proton-antiproton strong-interaction scattering length. Elastic and annihilation cross sections for ground-state hydrogen-antihydrogen scattering are calculated for s- and p-waves, and collision energies up to 1 atomic unit. The two methods are found to agree to within about 1%. The main source of discrepancy is that the scattering-length approach does not account for vacuum polarization, relativistic, and finite-size corrections. We verify that the range of the strong interaction potential does not affect the hydrogen-antihydrogen s-wave scattering properties, and that the strong interaction has negligible influence on p-wave scattering.
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68.
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69.
  • Jonsell, Svante, et al. (författare)
  • Low energy hydrogen-antihydrogen collisions
  • 2000
  • Ingår i: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 663-664, s. 959C-962C
  • 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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  • Resultat 61-70 av 116

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