K-LM radiative Auger effect in argon

The K–LM radiative Auger (RA) x-ray spectrum of argon was observed. The transitions were photoinduced by means of an x-ray tube and measured with two different high-resolution curved crystal spectrometers of reflection-type geometry. From the first measurements performed at the Paul Scherrer Institute (PSI), only an upper limit of 0.25% relatively to the intensity of the Kα1,2 diagram line could be obtained for the total K—LM RA yield. From a second experiment carried out at the University of Fribourg, a I(K–LM RA)/I(Kα1,2) ratio of 0.18±0.05% was obtained. This value is consistent with the PSI result but in strong disagreement with theoretical predictions based on the shake model, which are about four times larger. © 1998 John Wiley & Sons, Ltd.