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  • 1990-1994  (3)
  • 1975-1979  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2587-2590 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The enhanced plasma stopping of energetic (MeV/amu) multicharged ions is experimentally confirmed by inserting a fully ionized hydrogen column on a tandem accelerator ion beam line. Relevance to heavy ion driven inertial compression is emphasized. Measured energy losses are quantitatively matched by a theoretical extension of the cold matter stopping formula (Bethe).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 25.70.Gh ; 25.70.Jj ; 25.70.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For the violent collisions of 27 MeV/nucleon40Ar with Ag, coincidence measurements have been made between heavy residues and intermediate mass fragments (3≦Z≦14) or light charged particles. From the analysis of the correlation between heavy residues (mass and velocity) and intermediate mass fragments, the main characteristics of the dominant mechanisms, fusion and partially damped collisions preceded or accompanied by a preequilibrium emission, are presented. Balances concerning mean values of parallel linear momentum, mass and atomic number, are established and confirm that a complete description of violent collisions was obtained. Then thermalization is discussed, first in terms of excitation energies derived from kinematics between heavy residues and intermediate mass fragments, and secondly in terms of initial temperature estimates derived from light charged particle spectra. Very hot nuclei (T⋍5.7–6.6 MeV) are produced over a large impact parameter range from very central collisions to medium peripheral ones. Various experimental results are compared to predictions obtained with semi-classical calculations (Landau-Vlasov equation). From their good agreement one may conclude that, depending on the impact parameter, thermal equilibrium is achieved within 4–10×10−22 s.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The excitation functions for deep inelastic reactions in which two to six charges are transferred from40Ar and63Cu ions to rare earth targets have been measured using activation techniques, the observed radionuclides being150, 151Dy and149gTb. From the comparison of the curves relative to149gTb and those relative to150, 151Dy, it was deduced that the low spin isomer149gTb was produced with significant probability for low incident energies. Using data from (heavy ions,xn) reactions, it was possible to attribute this production to the deexcitation of Tb fragments formed in deep inelastic transfers with angular momenta lower than 9ħ. This result is in good agreement with the angular momentum calculations performed under the hypothesis that the initial angular momentum window leading to deep inelastic reactions is situated between the critical angular momentum for fusion and that corresponding to grazing collisions. As far as Cu induced reactions are concerned, both hypothesis of rolling and sticking are consistent with the experimental data. For Ar induced reactions, the results indicate that the stage of sticking is not reached when the incident energy is lower than 200 MeV. Nuclear Reactions:142, 145Nd,144, 148Sm,154Gd(Ar,X)151, 150Dy,149gTbE=160–280 MeV; measuredσ(E).144Nd,148Sm,151Eu,154Gd(Cu, X)151, 150Dy,149gTb.E=280–420 MeV measuredσ(E). Enriched targets. Deduced angular momentum of Tb fragments.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamics of the two partners produced in dissipative collisions has been experimentally studied for the system40Ar + Ag at 27 MeV per nucleon. Primary masses of the fragments can then be calculated; the excitation energy partition between the two fragments is derived from the number of particles evaporated by each fragment. We found that this division evolves from equipartition to a repartition close to thermal equilibrium in the excitation energy range 300–350 MeV or interaction times 5-10×l0−22 s.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured for the 430 MeV86Kr+92.98Mo systems the triple differential cross sectiond 3 σ/dEdAdZ (E=kinetic energy,A=mass andZ=atomic number) of the reaction products in the angular range (θ=25, 45°). We focussed attention on a fast collective mode in deep inelastic reactions: the neutron excess or charge equilibration. This mode is shown to relax very quickly to equilibrium within a time scale of the order of 10−22s. It is shown that this collective degree of freedom exhibit a quantal behavior which can be seen in the observation of quantal fluctuations. The experimental results are discussed in terms of a simple equilibrium model. The giant dipole resonance of the composite system could be closely connected to this neutron excess mode.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analysis of angular distributions for quasi-elastic transfer reactions is proposed. The formalism used is derived from the general treatment of multinucleon transfer in the limits of DWBA approximation. It appears that for heavy ions, the use of real potentials with real trajectories remains a good approximation in the window ofl space concerned with quasi-elastic transfer reactions. This analysis has been tested by a series of experimental data obtained by bombardment of209Bi targets by14N,16O,19F,40Ar and40Ca. For incident energies near the Coulomb barrier, the deflection angle depends strongly on the excitation energy of the system so that a window ofQ values leads to very wide angular distributions. A slow decrease of the radius parameter with the increase of theZ 1 Z 2 product has been observed. This result can be correlated by an interaction distance (d=2.7–3fm) between half density radii of the two colliding nuclei.
    Type of Medium: Electronic Resource
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