Angular correlations in near-threshold double photoionization of krypton

Double ionization of krypton leaving the ion in its ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}^{\mathit{e}}$ ground state has been studied at 2.26 eV above threshold, the two photoelectrons being measured in coincidence with angle and energy selection. The results are compatible with the angular dependence of the favored ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}^{\mathit{o}}$ state of the pair of electrons, which can be selected by maintaining the angle between the two detectors, ${\mathrm{\theta }}_{12}$, equal to 180°. The observed angular correlation is maximum at ${\mathrm{\theta }}_{12}$=180° and appears to originate from the three-body ion-electron-electron interaction, in qualitative agreement with the Wannier theory.