Low-Intensity First-Forbidden Beta-Decay Branch inCa45

Abstract

A weak [(${1.7}_{-0.3\mathrm{}}^{+0.8\mathrm{}}$)×${10}^{-5\mathrm{}}$ per decay] inner beta branch in the decay of 165-day ${\mathrm{Ca}}^{45}$ populates the ${12.47}_{-0.03\mathrm{}}^{+0.14\mathrm{}}$ keV state in ${\mathrm{Sc}}^{45}$, as established by the observation of the $K$ conversion electrons of this transition, superimposed on the 258±2 keV allowed ground-state beta continuum. The $log{f}_{1}t$ inferred for this probably first-forbidden unique ($\frac{7}{2}-\to \frac{3}{2}+$) inner group is ${9.28}_{-0.18\mathrm{}}^{+0.06\mathrm{}}$. No certain evidence was found for the $L$ lines; the $\frac{K}{L}$ ratio is given as $2\le \frac{K}{L}\le \infty$, with a most likely value of 5.