STRUCTURE OF NEUTRON-RICH NUCLEI AND NEUTRON MULTIPLICITIES IN SPONTANEOUS FISSION

New insights into the fission process and the structure of neutron-ric h nuclei have been gained by measuring gamma-gamma and gamma-gamma-gam ma coincidences of the prompt gamma-rays following the spontaneous fis sion of Cf-252. The data were taken with the Compton Suppression Spect rometer System at HHIRF. New high spin levels were observed in Ba-143, Ba-145,Ba-147. Only in Ba-143 are intertwined bands observed with the characteristics of the octupole structure found only in Ba-144. New hi gh spin states observed in the N = 84 Te-136, Xe-138, Ba-140 nuclei ex hibit a symmetry pattern suggestive of a pseudospin (f) over tilde-she ll. For the first time in fission, the relative yields and neutron mul tiplicities were measured directly, Yields and multiplicities were mea sured directly for the Zr-Ce and Mo-Ba correlated fragment pairs by ob serving the coincidences between the gamma-rays in each fragment. Zero -neutron to ten-neutron emission yields were determined; the latter fo r the first time. The zero-neutron emission can be understood as a new example of cluster radioactivity. These results demonstrate that the use of the high resolution gamma-gamma-gamma coincidence technique emp loyed here for the first time opens up a new approach to the study of the fission process that will provide previously inaccessible details of the process.