The decay of hot nuclei formed in La-induced reactions at E/A = 45 MeV

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7295993

Libby, B P

The decay of hot nuclei formed in the reactions [sup 139]La + [sup 27]Al, [sup 51]V, [sup nat]Cu, and [sup 139]La were studied by the coincident detection of up to four complex fragments (Z > 3) emitted in these reactions. Fragments were characterized as to their atomic number, energy and in- and out-of-plane angles. The probability of the decay by an event of a given complex fragment multiplicity as a function of excitation energy per nucleon of the source is nearly independent of the system studied. There is no large increase in the proportion of multiple fragment events as the excitation energy of the source increases past 5 MeV/nucleon. This is at odds with many prompt multifragmentation models of nuclear decay. Correlation functions of the relative velocity and angle between pairs of fragments in events with 3 complex fragments are similar to those of other reactions in which a sequential mechanism for the emission has been proposed. A fast-fission reaction mechanism may be occurring in the reaction La + Al (and possibly La + V). The reactions [sup 139]La + [sup 27]Al, [sup 51]V, and [sup nat]Cu were studied by combining a dynamical model calculation that simulates the early stages of nuclear reactions with a statistical model calculation for the latter stages of the reactions. For [sup 139]La + [sup 27]Al, these calculations reproduced many of the experimental features, such as fragment cross sections, and total charge and source velocity distributions for multiple fragment events. Other features were not reproduced. For [sup 139]La + [sup 51]V, the shape of the fragment cross section distribution, and the total charge and source velocity distributions were reproduced by the model. The calculation failed to reproduce the magnitude of the cross sections, charge-Dalitz plots, and branching ratios. The calculation failed to reproduce any experimental features of the reaction [sup 139]La + [sup nat]Cu, with the exception of the source velocity distributions.

• Research Organization: Maryland Univ., College Park, MD (United States)
• OSTI ID: 7295993
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
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NUCLEAR DECAY
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RADIOCHEMISTRY
VANADIUM 51 REACTIONS