Light fission-fragment mass distribution from the reaction 251Cf(nth, f )

For mass numbers A=80 to 124 the recoil mass spectrometer LOHENGRIN of the Institute Laue-Langevin in Grenoble was used to measure with high resolution the light fission-fragment mass yields and kinetic energy distributions from thermal-neutron induced fission of 252Cf* for the first time, using 251Cf as target material. The obtained mean light fragment mass 〈AL〉=(107±2) and the corresponding mean kinetic energy 〈Ek,L〉=(103±2) MeV are within the expected trend. Emission yields around A=115 are enhanced and the corresponding mean kinetic energy is higher compared to spontaneous fission of 252Cf. This could be explained by the existence of an additional super-deformed fission mode.