Binary fragmentations of F + Bi (E"=491 MeV) and Ni + Ho (E"=778 MeV) leading to compound nuclei with E* 400MeV and similar masses were investigated by measuring fission coincident neutrons and o. particles. The neutron 6eld was decomposed into contributions from preequilibrium (PE), prescission, and the two fragment sources with a moving source analysis. It was performed for separate excitation energy classes deduced with the folding angle technique from the linear momentum transfer. The angular distribution of the PE neutrons from the F + Bi reaction indicates a pronounced out-of-plane anisotropy that would result in an overestimation of the PE multiplicity by 37'Po for a measurement only in plane. The PE multiplicities and temperatures are interpreted by a delay in formation for the more symmetric entrance channel Ni + Ho, which is typical for quasi6ssion and in line with the enhancement of asymmetric mass splits. Prescission times derived from the neutron clock method extend from 30 x 10 s for Ni + Ho to 160 x 10 s for F + Bi. Here, a constant level density parameter of A/10MeV was used which is an outcome of the simultaneous measurement of o. emission temperatures. The prescission times are qualitatively discussed in terms of the reaction dynamics.PACS number(s): 25.70. 3j, 24.60.k

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Energy spectra and multiplicities of neutrons from the reaction system 838 MeV 32S projectiles on 197Au have been measured in coincidence with binary fragmentations. Neutron detection was performed simultaneously in a 4re scintillator sphere and by time-of-flight. The linear momentum transfer (LMT) and the excitation energy E~N are deduced with the folding angle technique. Neutron multiplicities are compared for consistency and discussed as a measure of LMT and E*N. The saturation of M4~(E*N) beyond E*N ~ 400 MeV seen for several systems of high fissility (x > 0.8) is attributed to the spreading of the folding angle distribution and the increasing competition of charged particle evaporation.

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