Mass and nuclear-charge yields for 249Cf(n th, f) at different fission-product kinetic energies

Abstract

The recoil mass spectrometer Lohengrin of the Laue-Langevin Institute, Grenoble, has been used to measure the yields of light fission products from 249Cf(n th, f) as a function of A, Z, the kinetic energies and the ionic-charge states. The mass and nuclear-charge distributions integrated over all the ionic-charge states were determined for different kinetic energies E Loh between 87 and 112 MeV. The behaviour of ΔZ = Z− Z UCD as a function of A' differs strongly from that for 236U and 240Pu; it passes the zero value at ~7.5 mass units away from the center of the Z = 50 shell and it reaches ΔZ ∼ 1 at A' ∼ 123 without ever passing the shell. The mean proton and neutron odd-even effects on yields are δ p = (4.6 ±0.7)% and δ n = (9.5 ±0.7)%. The odd-even effects on mean proton and neutron kinetic energies are δE K o−e ( Z) = (0.20 ± 0.07) MeV and δE K o−e ( N) = (0.48 ± 0.16) MeV, respectively. The mean value of isobaric variance 〈 σ Z 2〉 = (0.43 ± 0.03) and, unlike the results for 236U and 240Pu it shows little dependence on kinetic energy; the present value along with the results for the other fissioning nuclei confirm that σ Z 2 results from zero-point isovector giant dipole vibration at the exit point.