Radiative capture of 1s electrons in 204Tl

Previous measurements of the internal bremsstrahlung associated with the K-capture decay of ²⁰⁴Tl have ignored the contribution to the spectrum due to double internal bremsstrahlung from the β decay of ²⁰⁴Tl. We have measured the internal bremsstrahlung spectrum, using a two-parameter analysis to subtract this contribution. A fit to the data using the theory of Glauber and Martin and a relativistic correction factor $R_{1s}=0.29$ yields a transition energy of 385±20 keV. The ratio of the theoretical to the experimental intensity is 3.6.