Ionization Following Beta Decay in Krypton-85

Abstract

Following beta decay in the 9.4-year radioactivity of ${\mathrm{Kr}}^{85}$, the product rubidium atoms are found to be distributed in the following charge spectrum (figures in percent): charge 1, 79.2±1.0; charge 2, 10.9±0.2; charge 3, 3.9±0.1; charge 4, 3.1±0.1; charge 5, 1.51±0.07, charge 6, 0.66±0.04; charge 7, 0.40±0.02; charge 8, 0.19±0.02; charge 9, 0.093±0.01; charge 10, 0.026±0.006; charge 11, unobservable. An interpretation is made in terms of the "shaking off" of extranuclear electrons by the sudden change by +1 in the nuclear charge, the intensity of the charge-2 ions being taken as a direct measure of the probability of "shake-off" from the combined $4s$ and $4p$ shells. The combined intensities of charge 3 and higher are correspondingly equated to the summed probabilities of primary ionizations in the $n=1, 2, \mathrm{and} 3$ shells.