Higer order effects accompanying forbidden beta decay

In the process of electron capture by the nucleus an electron neutrino is emitted carrying away practically all available energy equal to Q-B, where Q is the decay energy and B is the binding energy of the captured electron. With the relative probability of the order of 10-4 the neutrino is accompanied by a photon. In this second-order radiative process (called internal bremsstrahlung - IB) the available energy is shared statistically between the neutrino and the photon, which results in a continuous energy spectrum of emitted photons. The aim of this paper is the IB process accompanying forbidden transitions, specifically those in which spin difference between initial and final nuclear states is equal to 2. Then, if the parities of those nuclear states are different, the authors have the first forbidden unique transition, otherwise (no change of parity) the transition is second forbidden nonunique (2nu)