HIGH ENERGY ZEROS AND OTHER TYPES OF ZEROS IN PHOTOIONIZATION

author  L. A. LaJohn and R. H. Pratt

Department of Physics and Astronomy, University of Pittsburgh,
Pittsburgh, PA 15260, USA

We discuss a class of zeros found at relativistic energies in photoionization
matrix elements. They occur in dipole $(n,l,j) \rightarrow (\epsilon ,l+1,j)$ transitions,
for energies greater than 100 keV, and they have observable physical consequences in
photon electron polarization correlations $C_{i j}$, especially $C_{23}$. We describe
properties of these zeroes and compare them with other classes of photoionization zeros.