Angular momentum in subbarrier fusion

Conference · Tue May 01 04:00:00 EDT 1990

OSTI ID:6706025

DiGregorio, D E; Lesko, K T; Harmon, B A; Norman, E B; Pouliot, J; Sur, B; Chan, Y D; Stokstad, R G

We have measured the ratio of the isomer to ground-state yields of {sup 137}Ce produced in the fusion reactions {sup 128}Te({sup 12}C,3n), {sup 133}Cs({sup 7}Li,3n), {sup 136}Ba({sup 3}He,2n), {sup 136}Ba({sup 4}He,3n), and {sup 137}Ba({sup 3}He,3n), from energies above the Coulomb barrier to energies typically 20--30% below the barrier by observing the delayed x- and {gamma}-ray emission. We deduce the average angular momentum, {lt}J{gt}, from the measured isomer ratios with a statistical model. In the first three reactions we observe that the values of {lt}J{gt} exhibit the behavior predicted for low energies and the expected variation with the reduced mass of the entrance channel. We analyze these data and the associated cross sections with a barrier penetration model that includes the coupling of inelastic channels. Measurements of average angular momenta and cross sections made on other systems using the {gamma}-multiplicity and fission-fragment angular correlation techniques are then analyzed in a similar way with this model. The discrepancies with theory for the {gamma}-multiplicity data show correlations in cross section and angular momentum that suggest a valid model can be found. The measurements of angular momentum using the fission fragment angular correlation technique, however, do not appear reconcilable with the energy dependence of the cross sections. This systematic overview suggests, in particular, that our current understanding of the relationship of angular momentum and anisotropy in fission fragment angular correlations is incomplete. 26 refs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6706025
• Report Number(s): LBL-29135; CONF-9005221--8; ON: DE90015721
• Country of Publication: United States
• Language: English

Related Subjects

651720* -- Nuclear Properties & Reactions
A=90-149
Experimental
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR MOMENTUM
BETA DECAY RADIOISOTOPES
CERIUM 137
CERIUM ISOTOPES
COULOMB FIELD
CROSS SECTIONS
DAYS LIVING RADIOISOTOPES
ELECTRIC FIELDS
ELECTRON CAPTURE RADIOISOTOPES
EVEN-ODD NUCLEI
HEAVY ION FUSION REACTIONS
HOURS LIVING RADIOISOTOPES
INTERNAL CONVERSION RADIOISOTOPES
ISOMER RATIO
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MATHEMATICAL MODELS
MULTIPLICITY
NUCLEAR REACTIONS
NUCLEI
RA
RADIOISOTOPES
RARE EARTH ISOTOPES
STATISTICAL MODELS