Decay Properties ofZr86

Abstract

A restudy of the radiations of 16.5-h ${\mathrm{Zr}}^{86}$ was carried out with lithium-drifted germanium and silicon detectors and with a NaI crystal spectrometer. Besides x rays, there are gamma rays of 28, 243, and 612 keV in relative intensity 21, 100, and 5.4. No other gamma rays were detected. No annihilation radiation was present. There is no evidence for formation of 48-min ${\mathrm{Y}}^{86m}$ in the decay of ${\mathrm{Zr}}^{86}$. The $K$-conversion coefficient of the 243-keV transition was found to be 0.035\ifmmode\pm\else\textpm\fi{}0.003. The lifetime was measured as 29\ifmmode\pm\else\textpm\fi{}3 nsec. These properties agree well with an $E2$ multipolarity. The lifetime and conversion coefficient of the 28-keV transition are 10 nsec and 3.8\ifmmode\pm\else\textpm\fi{}0.5, respectively, which corresponds to an $E1$ multipolarity. A decay scheme is constructed and reasonable shell-model assignments are made to all levels except the 2- level of ${\mathrm{Y}}^{86}$, whose character is uncertain.