DoubleKCapture and SingleKCapture with Positron Emission

Abstract

Transition probabilities are estimated for double $K$ capture and for single capture with single positron emission. With real neutrino emission, the mean lives for both processes should be greater than ${10}^{24}$ years. Without real neutrino emission, as with Majorana neutrinos, the mean life for $K$ capture in conjunction with positron emission is about ${10}^{15}$ years in the allowed approximation. Double $K$ capture, however, is then at least a third-order process because an additional step is necessary to remove the energy, with the result that the mean life exceeds ${10}^{18}$ years.