Search for the Expected Radiation due to Photoejection of an Inner Shell Electron

R. Pratt et al. have called attention to the unsettled observational status for the radiation (intraatomic bremstahlung, IAB) expected upon the photoejection of inner shell electrons. We tested for such radiation in the 3 to 7 keV band produced by photoelectrons from the K shell of a copper target upon absorption of an incident 46 keV photon. Exploiting a prediction for the major background process: ordinary bremsstrahlung due to the encounter of the photoelectron with atoms other than that of its point of origin, we conclude that for our thinnest (40 nm) targets within statistical limits we observe no IAB radiation. In this manner, contemporary theory is ruled out by over 5 sigmas. Assuming no particular secondary process the intensity of observed IAB radiation is 4 sigmas below expectations. We conclude that in contrast to the sister nuclear process of internal bremsstrahlung observed upon beta decay, our understanding of intratomic bremsstrahlung remains lacking.