Decay ofHo163

A sample of ${\mathrm{Ho}}^{163}$ was prepared by neutron irradiation of ${\mathrm{Er}}^{162}$ followed by chemical purification and isotope separation. This nuclide ${\mathrm{Ho}}^{163}$ appears to decay by electron capture from the $M$ and higher shells. A half-life of 33±23 yr has been estimated by counting the $M$ Auger electrons and $M$ x rays from a sample over a period of two years. A search for $L$ x rays has been made. The $M$-to-$L$ capture ratio is greater than 1040. From this datum the $Q$ value for electron capture can be deduced to be 9.1±1.5 keV.