Delayed-neutron emission from mass separated heavy fission products has been studied using a sensitive neutron counter. Twelve new delayed-neutron precursors have been found, namely ${}_{}{}^{122}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{123}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{127}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{128}{}_{}{}^{}\mathrm{Cd}$ (or ${}_{}{}^{128}{}_{}{}^{}\mathrm{In}_{}^m{}_{}{}^{}$), ${}_{}{}^{128}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{129}{}_{}{}^{}\mathrm{In}$ (two isomers), ${}_{}{}^{130}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{131}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{132}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{133}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{136}{}_{}{}^{}\mathrm{Sb}$. The half-life determination for 11 other precursors has been improved.

RADIOACTIVITY ${}_{}{}^{122,123}{}_{}{}^{}\mathrm{Ag}$, ${}_{}{}^{127-132}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{128}{}_{}{}^{}\mathrm{Cd}$, ${}_{}{}^{133,134}{}_{}{}^{}\mathrm{Sn}$, ${}_{}{}^{134-136}{}_{}{}^{}\mathrm{Sb}$, ${}_{}{}^{136}{}_{}{}^{}\mathrm{Te}$, ${}_{}{}^{137-141}{}_{}{}^{}\mathrm{I}$, ${}_{}{}^{141-146}{}_{}{}^{}\mathrm{Cs}$, measured delayed neutrons; deduced half-lives.

• Received 21 October 1975

DOI:https://doi.org/10.1103/PhysRevC.13.1544