Decay Scheme ofRb83

Abstract

We have re-examined the decay of ${\mathrm{Rb}}^{83}$, which is reported to decay by electron capture, with emission of a single $\gamma$ ray of 525 keV, to the 1.86-h isomer of ${\mathrm{Kr}}^{83}$. With the aid of a lithium-drifted germanium detector and with a high-resolution beta spectrometer we find that the 525-keV photopeak observed with NaI crystals is really a superposition of three $\gamma$ rays at 521 keV (46%), 530 keV (31%), and 553 keV (16%). An additional $\gamma$ ray was found at 790 keV with intensity of 0.9%. Various coincidence experiments showed that only the 521- and 530-keV transitions lead to the 1.86-h ${\mathrm{Kr}}^{83m}$. The 553- and 790-keV transitions lead to the 9.3-keV level of ${\mathrm{Kr}}^{83}$. Direct electron capture to this level has also been obsered with an intensity of 6%. The fraction of ${\mathrm{Rb}}^{83}$ disintegrations bypassing the isomeric state of ${\mathrm{Kr}}^{83}$ is 23%. The following new levels were assigned to ${\mathrm{Kr}}^{83}$: 562, 571, and 799 keV. The total disintegration energy of ${\mathrm{Rb}}^{83}$ was shown to be ≥825 keV.