Nonequilibrium effects in the /sup 139/La+/sup 40/Ar reaction at 10 MeV per nucleon observed in a study of neutron emission

Journal Article · Mon May 01 00:00:00 EDT 1989 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.39.1845· OSTI ID:6269181

Wile, J L; Datta, S S; Schroeder, W U; Huizenga, J R; Toke, J; de Souza, R T

Energy spectra of neutrons emitted in the damped reaction /sup 139/La+/sup 40/Ar at E/sub lab/ = 400 MeV were measured at eight angles in coincidence with projectile-like reaction fragments, using a time-of-flight technique. Apart from a small high-energy component, the angular and energy distributions of neutrons were found to be well described by assuming two sources moving at the velocities of the light and heavy reaction fragments emitting isotropically in their rest frames. The logarithmic slopes of the neutron energy spectra and the corresponding multiplicities of neutrons from the two sources suggest that the projectile-like fragment receives more than its equilibrium share of excitation energy for all values of total kinetic energy loss. Detailed statistical calculations indicate that the amount of excitation energy generated in each fragment is well described by the one-body nucleon exchange model. The high-energy component in the neutron energy spectra has properties that are consistent with preequilibrium neutron emission. Averaged over all energy losses greater than 20 MeV, this ''preequilibrium'' neutron multiplicity is approximately equal to 0.1. However, the intensity of this component increases as the impact parameter decreases.

• Research Organization: Departments of Chemistry and Physics and Nuclear Structure Research Laboratory, University of Rochester, Rochester, New York 14627
• OSTI ID: 6269181
• Journal Information: Phys. Rev. C; (United States), Vol. 39:5
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ARGON 40 REACTIONS
COMPOUND-NUCLEUS REACTIONS
LANTHANUM 139 TARGET
ANGULAR DISTRIBUTION
COINCIDENCE SPECTROMETRY
ENERGY SPECTRA
EVAPORATION MODEL
MEV RANGE 100-1000
MULTIPLICITY
NEUTRON EMISSION
PRECOMPOUND-NUCLEUS EMISSION
PROBABILITY
THERMAL EQUILIBRIUM
TIME-OF-FLIGHT METHOD
CHARGED-PARTICLE REACTIONS
DISTRIBUTION
EMISSION
ENERGY RANGE
EQUILIBRIUM
HEAVY ION REACTIONS
MATHEMATICAL MODELS
MEV RANGE
NUCLEAR MODELS
NUCLEAR REACTIONS
SPECTRA
TARGETS
651720* - Nuclear Properties & Reactions
A=90-149
Experimental