Atomic excitation caused by α decay of the nucleus: model study

When the nucleus of an atom decays by emitting an α particle, the surrounding electrons are disturbed and the atom may be ionized. Practically all calculations so far done for this ionization process are based on Migdal’s method in which the α particle is treated as a classical point charge that is emitted by the nucleus at a certain time. Migdal’s method yields the ionization probability that is in reasonable agreement with experiment. On the other hand, Kataoka et al indicated by means of a schematic model calculation that a fully quantum mechanical treatment of the α particle leads to the ionization probability much smaller than the one predicted by Migdal’s method. We reexamine Kataoka et al’s calculation by simplifying the model of the atom such that an exact calculation is feasible. We find that Migdal’s method can be approximately justified, and clarify the earlier analysis.