Non-dipole anisotropy parameters in the photoionization of Kr in the region of deep inner shell excitations

The photoelectron angular distribution (PAD) of the Kr 4p1/2 and 4p3/2 fine structure states was measured with linearly polarized synchrotron radiation in the vicinity of the resonant excitations of the 3p subshell. Experimental dipole and non-dipole anisotropy parameters were determined from the measured angular differential cross sections. In order to interpret our experimental results we have used a theoretical model going beyond the dipole approximation considering the quadrupole and octupole terms for the direct photoionization. We have taken into account several autoionization channels relevant for the studied photon energy range. The photon energy dependence of the measured anisotropy parameters puts in evidence the importance of the channel interactions. Moreover, unexpectedly large non-dipole contribution have been observed.