STRONG DYNAMICAL EFFECTS IN THE K-BETA-2 AND L-GAMMA-2,3 X-RAY-EMISSION SPECTRA OF LANTHANUM

The Kbeta1,3 (K --> M3,2), Kbeta2I,II (K --> N3,2) and the Lgamma2,3 (L1 --> N2,3) X-ray emission spectra from lanthanum have been measured, using high resolution crystal spectrometers. For the first time we observe an undisturbed 4p3/2 hole state together with a 4p1/2 hole state that is spread over an extended energy range. In comparison with theoretical calculations we show that in this case the quasi-particle picture only breaks down for the 4p1/2 core hole, due to very strong dynamical dipolar fluctuations and associated decay processes of the 4p1/2 core hole.