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.