Radiative electron capture in the first forbidden unique decay of 204Tl Original Research Article

The photon spectrum accompanying 1S electron capture in the first forbidden unique decay of 204Tl was measured. The total radiation intensity in the energy range from 100 keV to the spectrum end-point was found to be 2.8(2)×10−5 per K-capture, confirming a previously reported strong disagreement between the experiment and the internal bremsstrahlung theory for this nucleus. Contributions from detour transitions were not confirmed in the analysis.