Elsevier

Nuclear Physics A

Volume 462, Issue 1, 19 January 1987, Pages 85-108
Nuclear Physics A

235U(n, f) Fragment mass-, kinetic energy- and angular distributions for incident neutron energies between thermal and 6 MeV

https://doi.org/10.1016/0375-9474(87)90381-2Get rights and content

Abstract

Fission fragment energies and emission angles have been measured for 235U(n, f) in the neutron energy range from thermal to 6 MeV in steps of 0.5 MeV. The pre-neutron emission mass distributions were evaluated and described by a five-gaussian representation. The resulting parameters show a sudden change in their neutron energy dependence between 1.5 and 2.0 MeV, which might be due to pair breaking. From the total kinetic energy the sum of the deformations of the two fragments was evaluated. Clear proton pairing effects are visible since the even-proton fragments are less deformed than neighbouring odd-proton fragments. The present data confirm also that the TKE averaged over all fragments drops with excitation energy above 4 MeV. This behaviour is mainly due to drastic changes in TKE as function of mass split. At a yield level of 10−6 per MeV of the light fragment kinetic energy cold fragmentation was observed for light fragment masses 87 to 110. In this mass region the light fragments are prolate and have a ground state electric quadrupole moment larger than ≈1 b. The angular distributions of fission fragments showed no mass dependence.

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    Present address: Jydsk Technologisk Institut, Aarhus, Denmark.

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