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  • Electronic Resource  (9)
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  • Electronic Resource  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 292 (1979), S. 171-189 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract One-particle-inclusive measurements have been performed for the charge, kinetic energy and angular distributions of reaction products from238U +238U at 1 766MeV (7.42MeV/u) incident energy. The deep inelastic products exhibit features similar to those seen in reactions induced by medium heavy nuclei: increasing particle transfer is observed with increasing energy damping, the angular distributions are peaked near the grazing angle, they broaden significantly with increasing energy loss and/or charge transfer. The dominant reaction mechanism, however, is found to be sequential fission of one or both primary reaction products. The reconstructed primaryZ- andQ-value distributions show more particle transfer at a given energy loss than in other systems, i.e. the diffusion process seems to proceed colder in this system. This is confirmed by relatively large cross sections for surviving deep inelastic reaction products belowZ=92. A direct search forα-decay or fission of superheavy nuclei being produced in a deep inelastic reaction and being implanted in a surface barrier detector resulted in an upper cross section limit of 2 ×10−32cm2.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Reaction products corresponding to the transfer of one and several protons have been measured over a large angular range for incident energies of 380 MeV and 400 MeV in reactions of86Kr with88Sr,90Zr and92Mo. For transitions with smallQ-values (total kinetic energy loss TKEL≦10 MeV) the transfer probabilities are deduced. The magnitudes and slopes of these probabilities as function of the distance of closest approach between two nuclei are discussed. The results for single proton transfer are well described by tunneling, whereas the transfer of two and more nucleons into low lying states of the final nuclei seems to be influenced by intermediate transfer steps with larger TKEL. The data give the possibility to discuss the relation between deep-inelastic and quasi-elastic processes. The deep-inelastic data are analyzed successfully by including deformations, charge transfer and statistical fluctuations into the frictional model of Gross and Kalinowski.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 25.70.-z ; 25.70.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Events with 2, 3 and 4 heavy-fragments (A≧20) have been detected in the reactions100Mo+100Mo atE/A =18.7, 23.7 MeV and120Sn+120Sn atE/A=18.4 MeV. The experiments were performed with an array of 12 detectors which together covered a large fraction of the forward hemisphere and allowed a high detection efficiency for these events. Masses and energies of all fragments have been reconstructed by means of an improved version of the kinematic coincidence method. The probabilitiesP 3 andP 4 of producing 3- and 4-body events were found to depend mainly on the dissipated energy rather than on the bombarding energy, thus indicating that their origin lies more in the decay properties of the excited fragments than in the dynamics of the interaction. Emission of light particles from the composite system is shown to become more relevant with increasing bombarding energy and may explain the drop of theP 3 andP 4 curves at high energy losses. Small deviations of theP 3 andP 4 curves at 23.7A · MeV from those at lower bombarding energies were used to estimate the amount of a possible pre-equilibrium light particle emission as a function of impact parameter.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 283 (1977), S. 261-268 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Excitation functions and angular distributions have been measured for fission of238U induced by136Xe ions with bombarding energies between 4.5 and 5.9 MeV/N. Structures expected theoretically as characteristic for Coulomb fission have not been observed. The Q-value of −(7.5±1.0) MeV measured for bombarding energies below 4.7MeV/N, however, appears to be compatible with inelastic scattering (e.g. Coulomb excitation) rather than subcoulomb transfer followed by fission. The total kinetic energy of deep inelastic events at 5.9 MeV/N is consistent with the current knowledge about mass diffusion, but also (for the highest excitation energies) with a fast fission process in the presence of the projectile.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 295 (1980), S. 269-286 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The cross sections for production of evaporation residues (σ er) and for fusion-fission (σ ff) have been measured for40Ar+144, 148, 154Sm at sub-barrier energies by observation of x-ray emission from radioactive products and by direct,ΔE−E identification of fission fragments, respectively. These isotopes span the transition region from spherical (144Sm) to strongly deformed (154Sm) equilibrium shapes. The cross section for fusion,σ fus=σ er+σ ff, is found to vary markedly at low energies with the isotope number and, hence, with the quadrupole collectivity of the target. The thresholds for fusion of148Sm and144Sm are, respectively, ∼3.5 MeV and ∼7 MeV (c.m.) higher than for fusion with154Sm. These differences and the energy dependence of the fusion cross sections are discussed in terms of the effect of nuclear deformation on heavy-ion fusion. A comparative analysis of results for16O+Sm and40Ar+Sm in terms of static deformation indicates thatσ fus for the Ar+Sm system at very low energies is enhanced relative to the prediction for a one-dimensional barrier based on a fit toσ fus for16O+Sm. This may be an indication that additional degrees of freedom (such as formation of a neck or fragment elongation) may be important for fusion with the larger projectile. At energies above the fusion barrier, values ofσ fus for144, 148Sm are nearly equal, but are significantly smaller than for154Sm. This is in contrast to the results of previous experiments with16O projectiles in whichσ fus (16O+148Sm) andσ fus (16O+154Sm) were nearly equal above the barrier. These differences, observed for144, 148Sm and154Sm at energies above the barrier may reflect a new mechanism which is not encompassed by a static theory.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-601X
    Keywords: 25.70.Lm ; 25.85.−w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Events with 2, 3 and 4 heavy fragments (A≥20) detected in the reactions100Mo +100Mo at 18.7, 23.7 A·MeV and120Sn +120Sn at 18.4 A·MeV were analyzed by means of an improved version of the kinematic coincidence method. The phase-space distributions prove that 3- (and possibly 4-) body events predominantly originate from a two-step mechanism and are compatible with the hypothesis of a binary deep-inelastic interaction followed by the further fissionlike decay of one (or both) of the primary fragments. The characteristics of the fission step — mass asymmetry, relative velocity, in-plane and out-of-plane angles — have been reconstructed for the 3-body events and indications are found that nonequilibrium effects at the end of the deep-inelastic phase may influence the fissionlike decay.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 273 (1975), S. 211-219 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The two-neutron transfer reactionASn(18O,16O)A+2Sn has been measured for the isotopes A=112, 116, 118, 120, 122 and 124 at bombarding energies of 57 and 60 MeV together with the elastic scattering. Angular distributions have been analysed for the transitions to the ground state and to the first excited 2+ state. The observed ground state transition is strongly enhanced. The theoretical DWBA analysis is performed with a finite range 2n-transfer form factor including recoil correction. The calculated cross section reproduces the observed systematic change over all isotopes. The absolute cross sections are normalized by a factor of 4.7 and 7.5, depending on the two different sets of 2n-wave functions used in the analysis. The results confirm the prediction of the pairing model that the transition strengths of a neutron pair between the ground states of even tin isotopes are the same.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present data for the132Xe+56Fe-system at 5.73 MeV/u laboratory energy. Due to inverted kinematics, where Xe is the projectile, we were able to measure energy spectra as well as angular distributions for reaction products with 20≦Z≦60 with unitZ-resolution; i.e. target- and projectile-like fragments have been investigated. The reaction shows a well focussed quasielastic component, where charge transfer from the light to the heavy collision partner dominates. This apparent tendency towards more asymmetric fragmentation is explained by a potential energy surface which favours such charge transfer in order to minimize the asymmetry energy of the liquid drop. The strongly damped component which constitutes the major part of the reaction cross section exhibits characteristics of a fusion-fission reaction with typical fission fragment kinetic energies and 1/sinΘ c.m. angular distributions. The maximum cross section is found for the symmetric fragmentation, no clear indication is observed for a diffusion process leading to target- and projectile-like fragments. Our data are difficult to reconcile either with the standard diffusion models or with an equilibrated compound nucleus fission picture. We tentatively conclude that an essential part of the fully damped cross section originates from partial waves for which the compound nucleus has no fission barrier.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract First and second moments of primary charge distributions were determined as a function of the total kinetic energy loss in the reaction92Mo+92Mo at an incident energy of 14.7 MeV/u. Up to energy losses of 200 MeV no significant drift of the first moments is observed. The second moments are in agreement with predictions of a stochastic model derived at lower bombarding energies.
    Type of Medium: Electronic Resource
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