Investigation of the reaction 208 Pb( 18 O, f ): Folding angular distributions of fission fragments and gamma-ray multip
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CLEI Experiment
Investigation of the Reaction 208Pb(18 O, f ): Folding Angular Distributions of Fission Fragments and Gamma-Ray Multiplicity A. Ya. Rusanov1)* , M. G. Itkis2) , N. A. Kondratiev2) , I. V. Pokrovsky2), V. S. Salamatin2) , and G. G. Chubarian3) Received July 17, 2006; in final form, March 19, 2007
Abstract—Correlations between folding angular distributions of fission fragments and the gamma-ray multiplicity are studied for 18 O + 208 Pb interactions at energies of the beam of 18 О ions in the range Elab = 78–198.5 MeV. The probabilities are determined for complete- and incomplete-fusion processes inevitably followed by the fission of nuclei formed in these processes. It is found that the probability of incomplete fusion followed by fission increases with increasing energy of bombarding ions. It is shown that, for the incomplete-fusion process, folding angular distributions of fission fragments have a two-component structure. The width of folding angular distributions (FWHM) for complete fusion grows linearly with increasing energy of 18 О ions. The multiplicity of gamma rays from fission fragments as a function of the linear-momentum transfer behaves differently for different energies of projectile ions. This circumstance is explained here by the distinction between the average angular momenta of participant nuclei in the fusion and fission channels, which is due to the difference in the probabilities of fission in the cases where different numbers of nucleons are captured by the target nucleus. PACS numbers: 25.70.Jj, 25.70.Hi DOI: 10.1134/S1063778807100018
1. INTRODUCTION Incomplete-fusion processes play an important role in heavy-ion reactions. In this case, the transfer of mass and energy from the projectile ion to the target nucleus is only partial, with the result that the linear- [1–5] and angular-momentum [6–8] transfer from the former to the latter is also incomplete. For fissile nuclei, folding angular distributions of fission fragments [1–5, 9, 10] provide a good test for determining the linear-momentum transfer. The shapes and centroids of these distributions make it possible to evaluate the linear-momentum transfer and cross sections for complete and incomplete fusion (CF and ICF processes, respectively). The results of such investigations are summarized in the review articles quoted in [2, 11–13]. In addition to folding angular distributions of fission fragments, the authors of [14–18] also measured the neutron, 1)
Institute of Nuclear Physics, National Nuclear Center of the Republic of Kazakhstan, Almaty, 480082 Republic of Kazakhstan. 2) Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia. 3) Cyclotron Institute, Texas A & M University, MS no. 3366, College Station, TX 77843-3366, USA. * E-mail: [email protected]
proton, and alpha-particle multiplicities and their correlations with these distributions and showed that the multiplicities in question grow with increasing linear-momentum transfer (mass transfer), reaching a maximum value (total excitation energy of the compound nucl
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