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 3d(5/2) channel exhibits a pronounced minimum above threshold followed by a second maximum near the 3d(3/2) ionization onset and thus,qualitatively confirms the theoretical predictions of a spin-orbit activated interchannel coupling.