Electromagnetic and nuclear fission of238U in the reaction of 100, 500, and 1000 A�MeV208Pb with238U

Abstract

Abstract. The folding-and azimuthal-angle and velocity distributions for the Z3Su fission fragments have been measured in reactions with 100, 500, and 1000A.MeV 2~ These distributions were used to decompose the fission cross section into its electromagnetic and nuclear components. The fraction of electromagnetic fission was found to be 0.16-t-0.07, 0.48• and 0.60• respectively. The electromagnetic fission cross section as a function of the 2~ nucleus energy is compared with theoretical predictions. The measured fission cross section from nuclear reactions (~ 1.5 b) is approximately constant between 100 and 1000 A.MeV. 25.85.-w; 25.70.-z PACS:

Few-neutron removal from238U at relativistic energies

“…Using 2~ projectiles of 100, 500, and 1000 A MeV, these authors have determined the ED part of 238U (target) fission. By applying the same parametrization of fission decay after ED as discussed in the present paper, good agreement with the observed ED-fission cross sections has been found [13].…”

“…This indicates that the additional degree of freedom of the fission decay channel, which is absent in the ED of 197Au, is correctly taken into account for 238U. An independent corroboration of this fact comes from a direct experimental study of the fission process (which is complementary to neutron emission) by Polikanov et al [13]. Using 2~ projectiles of 100, 500, and 1000 A MeV, these authors have determined the ED part of 238U (target) fission.…”

“…(A comparison with the results of [21] shows similar agreement, but is less significant, since this data set does not extend far enough towards low energies). In both cases, however, a marked deviation between measured and calculated Pl~ values can be noted above [12][13][14][15] MeV. This excess cross section has been interpreted as evidence for a direct (non-statistical) In-emission process [21], which is definitely not contained in our statistical neutronevaporation model.…”

“…The data result from a first comprehensive study of 238U fragmentation performed at the GSI projectile fragment separator FRS [9][10][11][12]. They are complementary to results from an experiment studying target-like fission of a3aU induced by 2~ beams of energies between 100 and 1000 A MeV [13]. We will show below that all our measured :c~ cross sections can be interpreted consistently under the assumption of a simple harmonic oscillator model of giant resonances, in contrast to the study of neutron-removal from 197Au, where we had to invoke an increased DGDR excitation probability to reproduce the experimental cross sections [6,7].…”

Scaling laws inHe3induced nuclear fission

“…While the availability of relativistic heavy ions has enabled the study of several aspects of the fission process in the high energy region [2][3][4][5][6][7][8], it has been shown recently that a new approach [9] to investigate excitation functions of low energy, light particle induced fission allows for the model independent extraction of fundamental quantities of the fission process, like fission barriers, shell effects, and the much discussed fission delay time (see e.g. Refs.…”