Characterization of Hot Compound Nuclei from Binary Decay into Complex Fragments

Abstract

The emission of complex particles at intermediate energies has been characterized through the reverse-kinematics reactions 25-and 30-MeV/u ^-^Nb + ^Be, ^''Al. Complex particles observed in binary decays from very hot incomplete-fusion intermediates are shown to originate from compound-nucleus decay, by means of kinetic energies, angular distributions, and absolute yields. The process of complex-particle emission provides a method, applicable throughout the Periodic Table, for studying compound nuclei with temperatures and excitation energies near the expected limit of their existence.

Study of the fusion-fission process in the 35Cl +24Mg reaction

“…Calculations have already been performed for a previous publication [16,17]. In the following the full transition-state model calculations with sequential decay and using the GEMINI code [44] will be labeled as TSM. The main limitation of this code is the lack of reasonable mass-asymmetry dependence of the fission barriers for light nuclei.…”

“…The first model are for calculations based upon the transition-state theory [4,44] and for which the fission width is assumed to depend on the available phase space of the saddle point. Calculations have already been performed for a previous publication [16,17].…”

Complex fragment emission at 50 MeV/u: Compound nuclei forever?

“…However, in agreement with an earlier theory [9], complex fragment emission from a compound nucleus has been observed at very small incident energies, below 50 Me V total center-of-mass energy, albeit with very low (submicrobarn) cross-sections [10][11][12]. Furthermore, in a series of experiments starting at this low energy and continuing to 30 MeV/u, it has been verified that the decay of an equilibrated compound nucleus can account for the major production of complex fragments in a process akin to fission [13]. The measured excitation functions with their rapid rise near the barrier and their subsequent flattening at higher energies, together with thermalized kinetic energy spectra and 90· symmetric angular distributions, are quantitatively consistent with compound nucleus decay.…”

“…The continuity of these processes as a function of bombarding energy is exhibited by the fact that figure l(a) is virtually identical to figure l(b,c). Extensive analysis of the data at these lower energies has proven that fragments with Z ~ 12 arise from the binary decay of a compound nucleus formed either in a complete or incomplete fusion process [13,17]. In figure 2(b,c,d).…”

Complex fragment emission at intermediate energies

“…In a series of experiments (3,4,5), we have studied complex fragment production at progressively larger bombarding energies. The energies studied range from 8.4 MeVfu to 50 MeV/u, which is the highest bombarding energy studied at present.…”