$K$-Capture - Positron Ratios for the First-Forbidden Transitions of ${\mathrm{Rb}}^{84}$ and the Relative Probabilities of $L$- and $K$- Electron Capture

The radiations from ${\mathrm{Rb}}^{84}$ have been investigated by means of scintillation coincidence spectrometer techniques in order to obtain the relative intensities of the various transitions. The energies and abundances of the radiations are 0.44-Mev ${\beta }^{-}$ (5%), 0.81-Mev ${\beta }^{+}$ (10%), 1.70-Mev ${\beta }^{+}$ (9%), 0.89-Mev $\gamma$ (64%), and 1.91-Mev $\gamma$ (0.9%). [Note added in proof.—The ${\beta }^{-}$ has been shown to be 0.91 Mev (2.5%).] Electron capture populates the level 1.91 Mev above the ground state, competes (54%) with the 0.81-Mev ${\beta }^{+}$ to populate the level 0.89 Mev above ground, and competes (21%) with the 1.70-Mev ${\beta }^{+}$ in effecting transitions to the ground state of ${\mathrm{Kr}}^{84}$. The ratios of $K$-capture to positron emission for the transition to the 0.89-Mev level ($\Delta I=0\mathrm{}$, yes) and to the ${\mathrm{Kr}}^{84}$ ground state ($\Delta I=2\mathrm{}$, yes) are 5.15±0.38 and 2.06±0.36, respectively. These values are in qualitative agreement with theory. Nucleon configurations of the several states of ${\mathrm{Rb}}^{84}$, ${\mathrm{Kr}}^{84}$, and ${\mathrm{Sr}}^{84}$ are discussed. In the decay to the 0.89-Mev level an $\frac{L}{K}$-capture ratio of 0.12±0.05 was obtained by use of a value, 0.65, for the fluorescence yield of krypton. Alternatively, an experimental value for the fluorescence yield, 0.62±0.03, may be computed if the theoretical $\frac{L}{K}$-capture ratio is assumed.