SHORT-LIVED ISOMERIC STATES OF POLONIUM

Abstract

Two new nuclear isomeric states have been discovered in Po 207 by the reaction Bi 209 (p,3n)Po 207m , and additional information has been found on a previously discovered isomer in Po 205 produced by the reaction Bi 209 (p,5n)Po 205m . A 47-μsec activity was found in Po 207 which was assigned as the decay of a 13/2+ level by 310-kev M2 radiation to a 9/2− level, followed by an 820-kev E2 -γ-ray to the 5/2− ground state. The 13/2+ level in this nucleus was found to be fed by a 2.8-sec isomeric state which was assigned to the decay of a 19/2− level by 260-kev E3 radiation. A new 160-kev γ-ray was discovered in the Po 205 isomer. This isomerism is caused by a 13/2+ state which decays by a 160-kev M2, 707-kev E2 cascade to the 5/2− ground state through a 9/2− level. The various multipolarity assignments are supported by measurements of intensities, lifetimes, and K conversion coefficients. The levels found are compared with similar levels in analogous nuclides of lead.