Precision determination of charge dispersion and distribution in the proton-induced fission of238U at 13.9MeV excitation

Abstract

By means of a gas-jet transport system and the ordinary radiochemical stacked-target technique incorporated with the Geγ-ray spectrometry, 126 product nuclides with half-lives ranging from seconds through a year were identified and their yields were determined in the proton-induced fission of238U at 13.9 MeV excitation. The charge dispersion width was determined for mass chains and concluded to be constant with respect to the mass. The average of the deduced widths was 0.69±0.04 charge unit which was just equal to that of thermal-neutron fission of235U and also consistent with values reported for proton-induced fission of238U. From the width thus obtained, we determined the most probable chargesZ p for observed isobaric multiplets. Considering the pre-scission neutron systematics and an appropriate charge polarization between the complementary fragments we deduced from the obtainedZ p the post-scission neutron numberν post that turned out fairly consistent with Terrell’s neutron systematics for thermal-neutron-induced and spontaneous fission. Thus obtainedν post enabled us in turn to derive equations describingZ p as functions ofA. The obtained charge dispersion and charge distribution resulted in the mass-yield distribution resembling that of thermal-neutron fission.