Sudden interchannel interaction in the Tl 6p ionization above the 5d threshold

The Linear magnetic dichroism in the angular distribution of Tl 5d and 6p p hotoelectrons and their dynamical spin polarization have been measured betw een h nu = 30 and 50 eV. In contrast to the Xe 5p photoionization at the 3d threshold, our results show that above the Tl 5d threshold strong intercha nnel coupling effects induce a sudden increase in the asymptotic phase diff erence of the s and n waves for the Tl 6p ionization. This shows that the v alence excitation is different for resonant (Xe 4d) and nonresonant (Tl 5d) excitation from subvalence shells.