Electron-correlation effects in the angular distribution of photoelectrons from Kr investigated by rotating the polarization axis of undulator radiation

The angular anisotropy parameter beta for the 3p and 3d photoionization of krypton was investigated in the photon energy range from 325 eV to 1000 eV. Using the new UE52 undulator at the BESSY II storage ring the results were obtained by rotating the polarization axis of the linearly polarized synchrotron radiation. With this method high-precision measurements of beta are possible, showing significant deviations between experiment and theoretical calculations. This gives strong evidence for the importance of intrachannel and interchannel electron correlations for the photoionization processes of Kr.