Isospin dependence of intermediate mass fragment production in heavy-ion collisions at {ital E}/{ital A}=55 MeV
- Department of Chemistry, Washington University, St. Louis, Missouri 63130 (United States)
- Department of Physics and Astronomy and the National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States)
- Department of Chemistry and the Nuclear Structure Research Laboratory, University of Rochester, Rochester, New York 14627 (United States)
- Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)
The production of intermediate mass fragments (IMF{close_quote}s) from the four reactions 55{ital A} MeV {sup 124,136}Xe + {sup 112,124}Sn is studied with an experimental apparatus which is highly efficient for the detection of both charged particles and neutrons. The IMF{close_quote}s are more localized in the midvelocity region than are the light charged particles, and the detected multiplicity of IMF{close_quote}s depends linearly on the charge lost from the projectile and increases with the neutron excess of the system. Remnants of the projectile, with very little velocity reduction, are found for most of the reaction cross section. Isotopic and isobaric fragment yields in the projectile-velocity region indicate that charge-to-mass ratio neutralization is generally not achieved but is approached when little remains of the projectile. For all systems, the fragments found in the midvelocity region are substantially more neutron rich than those found in the velocity region dominated by the emission from the projectile. This observation can be accounted for if the midvelocity source (or sources) is either more neutron rich or smaller, with the same neutron-to-proton ratio, than the source with the velocity of the projectile. Taken together, the observations of this work suggest that the intermediate mass fragments are, to a large extent, formed by multiple neck rupture of the overlap material, a process which might enhance the neutron-to-proton ratio of the primary source material and/or limit the size of the sources. This scenario is reminiscent of low-energy ternary fission and one predicted by Boltzmann-Uehling-Uhlenbeck calculations. However, these calculations predict too much velocity damping of the projectile remnant. The calculations improve, in this regard, when the in-medium nucleon-nucleon cross sections and the cost of creating low density material are reduced. {copyright} {ital 1996 The American Physical Society.}
- Research Organization:
- Washington University
- DOE Contract Number:
- FG02-87ER40316; FG02-88ER40414
- OSTI ID:
- 390395
- Journal Information:
- Physical Review, C, Vol. 54, Issue 4; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
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