Decay ofSr85andSr85m

Abstract

${\mathrm{Sr}}^{85}$ (65 day) decays by $K$-capture to an excited state of ${\mathrm{Rb}}^{85}$ of 513-kev energy. This state is found to have a half-life of (0.9±0.2) μsec. It decays to the ground state of ${\mathrm{Rb}}^{85}$ by an $M2\mathrm{}$ transition, identified by its internal conversion coefficient. ${\mathrm{Sr}}^{85m}$ (70 min) decays in three ways: 14 percent by $K$-capture to an excited state of ${\mathrm{Rb}}^{85}$ of 150 kev, 84.7 percent by an $E3\mathrm{}$ transition of 7.5±1 kev followed by an $M1\mathrm{}$ transition of 225 kev, and 1.3 percent by an $M4\mathrm{}$ crossover transition of 232.5 kev. A decay scheme for ${\mathrm{Sr}}^{85}$, ${\mathrm{Rb}}^{85m}$, and ${\mathrm{Sr}}^{85m}$ consistent with shell theory and isomer systematics is given. The existence of large $\mathrm{ft}$ values for allowed $\beta$-transitions near closed shells is interpreted as due to a rearrangement of nucleons in the even-even core of an odd $A$ nucleus.