Observation of a 193-Millimicrosecond Metastable Level inPu239

Abstract

A metastable level in ${\mathrm{Pu}}^{239}$ with a half-life of 193 mμsec has been observed in the beta decay of ${\mathrm{Np}}^{239}$. This metastable state is assigned to a level 382 kev above the ground state of ${\mathrm{Pu}}^{239}$, and appears to de-excite by parallel 61- and 105-kev $E1\mathrm{}$ gamma transitions.