Detour transitions in forbidden radiative electron capture decay

The observed excess of electromagnetic radiation accompanying the first forbidden unique electron capture in 41Ca and the second forbidden nonunique electron capture in 59Ni is interpreted as the contribution of detour transitions via virtual nuclear states. Contrary to previous theories, we suggest that this contribution is important for forbidden transitions in the whole range of photon energies. New formulae for the shape factors of the spectra including the detour transitions are presented. The influence of nuclear structure on the intensity of the detour transition is discussed.