Interference effects in inner-shell double photoionization of xenon

We present measurements and calculations of triple differential cross sections (TDCSs) for indirect double photoionization of xenon due to inner-shell ionization and Auger decay. The interference effects, which occur when the energies of the photoelectron and Auger electron are equal to each other, are studied extensively by exploring several Auger lines. The related TDCS patterns appear to be governed by the symmetry of the residual ion: for antiparallel emission the interference is destructive for all states of symmetry, whereas it is observed for the first time to be constructive for the state of symmetry which has been selected. The calculated TDCSs, which are based upon expressions derived by Vegh and Macek (Vegh L and Macek J H 1994 Phys. Rev. A 50 4031) and on asymmetry parameters for the Auger and photo-electrons given in the literature, appear to be in good agreement with the experiments and allow us to investigate the interference effects in more detail.