DELAYED NEUTRON EMISSION IN DECAYS OF SHORT-LIVED SEPARATED ISOTOPES OF GASEOUS FISSION PRODUCTS

Delayed-neutron activity of separated isotopes of krypton and xenon and their decay products has been studied. The TRISTAN on-line isotope separator system at the Ames Laboratory Research Reactor was used to provide sources of short-lived gaseous fission products of selected masses, through A=93 for krypton and A=142 for xenon. Total delayed-neutron yields for each mass were measured by a calibrated long counter, and the relative yields of the parent and daughter nuclei in an isobaric decay chain were determined by multiscaling the delayed-neutron activity and resolving the contributions for different half-lives. The precusors and delayed neutron emission probabilities determined in this study are Kr92, 0.040%; Rb92, 0.012%; Kr93, 2.60%; Rb93, 1.65%; Xe141, 0.054%; Cs141, 0.073%; Xe142, 0.45%; and Cs142, 0.27%. A comparison is made between predictions for delayed-neutron emission from several semiempirical mass formulas and observations for isotopes of As, Br, Kr, Rb, Sb, I, Xe, and Cs. © 1969 The American Physical Society.