A study of statistical equilibrium in a nuclear system at low bombarding energies

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:5910088

Lee, Jeong Ho

The authors has studied a reaction of {sup 40}Ar + {sup 12}C at E/A = 8, 10, and 12 MeV. Fragments ranging from the lithium isotopes to the titaniums were detected at small forward angles ({theta} {approx} {plus minus}11{degrees}). Gamma-rays in coincidence with these fragments were also observed. The analysis of source velocities and simultaneous events suggests a characterization of complex fragment emission as a binary-decay process of the compound nucleus. In order to investigate whether the composite system formed from the projectile and the target ever reaches statistical equilibrium, the new temperature measurement proposed by Morrissey et al. has been applied to complex fragments including fragments of A > 10 for the first time. Temperatures of 2-3 MeV, which roughly agree with those from the Fermi gas model under the assumption of thermal equilibrium, were obtained from the {sup 7}Li, {sup 7}Be, and {sup 10}B at E/A = 8 and 10 MeV, however temperatures from the fragments of A > 10 show a fluctuation from nucleus to nucleus and also from transition to transition in the same nucleus. For the heavy residual fragments, the observed relative populations of nuclear states are compared with those predicted by the CASCADE statistical model. The result suggests that heavy fragments with masses close to the total mass in the reaction are produced from the compound nucleus by the statistical emission of light particles, such as nucleons and alpha-particles. However, the relative populations of nuclear states for fragments of Z < 20 show discrepancies between the observations and the predictions of the statistical model.

• Research Organization: Michigan State Univ., East Lansing, MI (USA)
• OSTI ID: 5910088
• Country of Publication: United States
• Language: English

Related Subjects

651320* -- Nuclear Properties &amp; Reactions
A=6-19
Experimental
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ARGON 40 REACTIONS
CARBON 12 TARGET
CHARGED-PARTICLE REACTIONS
COMPARATIVE EVALUATIONS
COMPOUND-NUCLEUS REACTIONS
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY RANGE
FERMI GAS MODEL
GAMMA RADIATION
HEAVY ION REACTIONS
IONIZING RADIATIONS
MASS
MATHEMATICAL MODELS
MEV RANGE
NUCLEAR FRAGMENTS
NUCLEAR MODELS
NUCLEAR REACTIONS
RADIATIONS
STATISTICAL MODELS
TARGETS