Beta Spectrum ofKr87

A measurement of the $\beta$ spectrum of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Kr}$ was undertaken to resolve some discrepancies in recently reported values of the branching of the $\beta$ decay to the ground state of ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$. Sources of mass-separated ${}_{}{}^{87}{}_{}{}^{}\mathrm{Kr}$, provided by the TRISTAN on-line isotope separator, were investigated with a high-resolution $\pi \sqrt{2}$ magnetic spectrometer. Using constraints based on previous $\gamma$-ray decay schemes, the measurement yielded a $Q$ value of 3.888 ± 0.007 MeV and a ground-state $\beta$ intensity of (30.5 ± 2.2)%. In addition, the intensity ratio for an unresolved $\gamma$-ray doublet at 2555 keV was independently determined on the basis of $\beta$-branch intensities to the levels at 2555 and 2960 keV.