Abstract
A study of the production and de-excitation of highly excited nuclei in the reactions of 261 and 490 Mev 14N + 154Sm is presented. Momentum transfer measurements show the most probable fraction of momentum transfer to be generally consistent with earlier systematics, however a dependence of momentum transfer on the target mass is observed. Gamma-ray multiplicity measurements indicate that at excitation energies near 200 Mev the angular momenta of residues surviving fission are lower than the accepted liquid drop model limits while at excitation energies approaching 400 Mev the angular momenta of residues surviving fission are larger than the liquid drop model limits. An interpretation in terms of the temperature dependence of fission and of particle evaporation is suggested. Comparisons of the transferred angular momenta to two models which predict angular momentum transfer show a microscopic geometric overlap model to be more appropriate at higher energies. Temperatures are extracted from the α-particle evaporation energy spectra observed at large center of mass angles and level density parameters are calculated. An evolution of the level density parameter from a [double turn] A/8 at excitation energies up to 200 Mev to a [double turn] A/13 at excitation energies of 400 Mev is observed. Implications of this trend are discussed. Energy spectra of α-particles calculated using the statistical model show good agreement with the measured energy spectra when the excitation energy variation of the level density parameter is explicitly included.
Hagel, John Christopher (1986). A study of the properties and de-excitation of highly excited nuclei. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -23602.