9317934 Samson Photoionization and double photoionization studies will be used to elucidate the effects of electron-electron correlation and spin-orbit effects in atoms. Of particular interest is the recent discovery that Compton electrons can produce ionization in atoms at high energies comparable to the direct photoionization process. Experimental measurements to unravel the details of these processes are important for a basic understanding of atomic photoabsorption and have pragmatic implications for plasma and astrophysical science.