The internal bremsstrahlung spectra from the EC beta decay of 193Pt and 163Ho

Internal bremsstrahlung spectra following electron-capture (EC) beta decay have been calculated in two versions of an extended Glauber-Martin theory. The case of 193Pt which has a Qsub(EC)-value that falls 20 keV below the 1s resonance point, is ideally suited for a test of this theory. The experimental data, both singles and L x-ray-bremsstrahlung coincidences, show that all the main features of the spectra are understood, although the absolute intensities agree to within a factor 1.5-2 only. The same calculations have been applied to 163Ho, with a Qsub(EC) of 2.82 keV, one of the main cases for an accurate measurement of the electron neutrino mass. The predicted occurence of an interference minimum near the end-point, however, makes the m(νsub(e)) experiment less attractive than one might have hoped for. (orig.)