Continuous Electron Spectrum AccompanyingKCapture

The continuous electron spectrum accompanying $K$ capture has been observed, in the case of ${\mathrm{Cs}}^{131}$, in three different ways: by measuring coincidences between one $K$ x-ray and an electron, by measuring coincidences between two $K$ x-rays and an electron, and by measuring the single electron spectrum. Furthermore, coincidences between two $K$ x-rays have been measured. The coincidence data were taken with scintillation counters while the single electron spectrum was taken with a magnetic spectrometer. The electron spectrum, including the absolute intensity, and the probability for a double hole in the $K$ shell are both found to be in agreement with the theory of Primakoff and Porter.