HALF-LIFE MEASUREMENTS OF RB, SR, Y, CS, BA, LA AND CE ISOTOPES WITH A=91-98 AND A=142-149

Half-lives of the extremely neutron-rich isotopes Rb91-98, Sr94-98, Y96-98, Cs142-146, Ba143-148, La144-149, and Ce149 were determined. The isotopes Ba147,148, and La149 were identified for the first time and their half-lives measured. The values obtained, in seconds, are 0.72±̂>0.07 for Ba147, 0.47±̂>0.20 for Ba148 and 1.2±̂>0.4 for La149. The other measured half-lives either confirm or improve previous measurements. An extrapolation procedure based on the systematic behavior of experimental half-lives for the prediction of half-lives not yet measured was used. Similar systematic behavior is also apparent for half-lives predicted within the framework of the gross theory of ̂> decay. RADIOACTIVITY Rb91-98, Sr94-98, Y96-98, Cs142-146, Ba143-148, La144-149, Ce149 [from U235 (n, fission)]; measured T12. Si surface barrier detector. Mass-separated Rb, Sr, Cs, and Ba activities. © 1979 The American Physical Society.