FISSION YIELDS OF THE STABLE AND LONG-LIVED ISOTOPES OF CESIUM, RUBIDIUM, AND STRONTIUM AND NUCLEAR SHELL STRUCTURE

The relative yields of the isotopes of cesium, rubidium, and strontium from thermal neutron fission of U235 have been determined mass spectrometrically. The cesium isotope yields are combined with those obtained previously for the xenon isotopes to give high precision yields for mass chains from 131 to 137. In this work neutron capture reactions have been considered and corrections made where these take place to an appreciable extent. The results give further evidence of abnormal yields in the 82 neutron shell region. The half-life of Cs137 was determined and found to be 33 ± 2 years.