85 research outputs found
Fission Decay Widths for Heavy-Ion Fusion-Fission Reactions
Cross-section and neutron-emission data from heavy-ion fusion-fission
reactions are consistent with a Kramers-modified statistical model which takes
into account the collective motion of the system about the ground state; the
temperature dependence of the location of fission transition points; and the
orientation degree of freedom. We see no evidence to suggest that the nuclear
viscosity departs from the surface-plus-window dissipation model. The strong
increase in the nuclear viscosity above a temperature of ~1 MeV deduced by
others is an artifact generated by an inadequate fission model.Comment: 14 pg, 6 fig, submitted to Physical Revie
Black-body photon clustering by semi-classical means
If stimulated emission could be turned off then only uncorrelated photons
would be emitted from black bodies and the photon counting statistics would be
Poissonian. Through the process of stimulated emission, some fraction of the
photons emitted from a black body are correlated and thus emitted in clusters.
This photon clustering can be calculated by semi-classical means. The
corresponding results are in agreement with quantum theory.Comment: 10 pages, 2 figures, 1 table. Added proof that stimulated-emission
produced photon clustering at the source leads to the Hanbury Brown and Twiss
effect without invoking photon-photon interference. Fixed unit mistakes in
the left hand side of Eqs (4), (6), (7), and (9
An evaporation-based model of thermal neutron induced ternary fission of plutonium
Ternary fission probabilities for thermal neutron induced fission of
plutonium are analyzed within the framework of an evaporation-based model where
the complexity of time-varying potentials, associated with the neck collapse,
are included in a simplistic fashion. If the nuclear temperature at scission
and the fission-neck-collapse time are assumed to be ~1.2 MeV and ~10^-22 s,
respectively, then calculated relative probabilities of ternary-fission
light-charged-particle emission follow the trends seen in the experimental
data. The ability of this model to reproduce ternary fission probabilities
spanning seven orders of magnitude for a wide range of light-particle charges
and masses implies that ternary fission is caused by the coupling of an
evaporation-like process with the rapid re-arrangement of the nuclear fluid
following scission.Comment: 25 pages, 12 figures, accepted for publication in IJMP
Quasi-fission reactions as a probe of nuclear viscosity
Fission fragment mass and angular distributions were measured from the
^{64}Ni+^{197}Au reaction at 418 MeV and 383 MeV incident energy. A detailed
data analysis was performed, using the one-body dissipation theory implemented
in the code HICOL. The effect of the window and the wall friction on the
experimental observables was investigated. Friction stronger than one-body was
also considered. The mass and angular distributions were consistent with
one-body dissipation. An evaporation code DIFHEAT coupled to HICOL was
developed in order to predict reaction time scales required to describe
available data on pre-scission neutron multiplicities. The multiplicity data
were again consistent with one-body dissipation. The cross-sections for touch,
capture and quasi-fission were also obtained.Comment: 25 pages REVTeX, 3 tables, 13 figures, submitted to Phys. Rev
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