Observation of the spin-orbit activated interchannel coupling in the 3d photoionization of caesium atoms

The ionization cross-section of the 3d spin–orbit components of the Cs atom has been measured from about 12 to 70 eV above their respective thresholds. The measured relative ionization cross-section of the 3d5/2 channel exhibits a pronounced minimum above threshold followed by a second maximum near the 3d3/2 ionization onset and thus qualitatively confirms the theoretical predictions of a spin–orbit activated interchannel coupling (Amusia et al 2002 Phys. Rev. Lett 88 093002).