Emission of unstable clusters from hot Yb compound nuclei

Journal Article · Thu Feb 01 04:00:00 EST 2001 · Physical Review C

DOI:https://doi.org/10.1103/PhysRevC.63.024611· OSTI ID:40206139

Charity, R J; Sobotka, L G; Cibor, J; Hagel, K; Murray, M; Natowitz, J B; Wada, R; El Masri, Y; Fabris, D; Nebbia, G ^[1]

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1. and others

Neutrons and isotopically resolved light charged particles have been detected in coincidence with evaporation residues produced in the reaction E/A=11 MeV {sup 60}Ni+{sup 100}Mo. Multiplicities of evaporated particle-unstable clusters have been determined from correlations in the emission of these light particles. The decay of the short-lived {sup 5}He and {sup 8}Be (E{sup *}=3.04 MeV) states was found to be affected by the Coulomb field of the compound nucleus in accordance with theoretical estimates. The contributions to the measured kinetic-energy distributions of stable fragments from the sequential decay of the unstable clusters was examined. Overall, the contributions from secondary fragments do not greatly influence the spectral shapes and specifically the location of the spectral peaks are not significantly shifted down in energy due to the presence of these secondary fragments. Therefore contrary to the suggestion of Charity [Phys. Rev. C 56, 873 (1997)], the lower peak energy of the experimental {alpha}-particle spectrum as compared to standard statistical-model calculations cannot be attributed to sequential {alpha} particles from {sup 5}He and other clusters. Only for the extreme ''subbarrier'' regions of the {alpha}-particle, deuteron, {sup 6,7}Li, and {sup 8}Be spectra was the sequential contribution found to be dominant. Statistical-model calculations incorporating large initial deformations are shown to provide enhancements in the yield of low-energy fragments which are roughly appropriate for all the detected isotopes. This suggests that the origin of the sub-barrier enhancements may be a result of evaporation from highly deformed systems which are either produced dynamically during the fusion process or by thermal shape fluctuations.

• Sponsoring Organization: (US)
• OSTI ID: 40206139
• Journal Information: Physical Review C, Journal Name: Physical Review C Journal Issue: 2 Vol. 63; ISSN 0556-2813
• Publisher: The American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
CHARGED PARTICLES
COMPOUND NUCLEI
COULOMB FIELD
DECAY
EVAPORATION
FLUCTUATIONS
KINETIC ENERGY
NEUTRONS
ORIGIN
RESIDUES
SHAPE
SPECTRA