INNER-SHELL IONIZATION OF ATOMS BY ELECTRON, POSITRON AND PHOTON IMPACTS

Plane wave Born approximation with Coulomb, relativistic and exchange corrections is employed to obtain L1-, L2- and L3- subshell ionization cross sections of several atoms due to electron and positron impacts for projectile energy varying from the threshold of ionization to 60 t imes the threshold energy. Photoionization cross sections for all the three L-subshells of the atoms are also calculated using the hydrogeni c approximation for the atomic wave functions. For L3-subshell the pre sent cross sections due to electron impact are in good agreement with a number of experimental data for different atoms over the entire ener gy range investigated. For L1- and L2-subshells the present calculatio ns yield qualitative agreement with the experimental data. The agreeme nt between the present results and the limited experimental data for p ositron impact is also satisfactory. The hydrogenic approximation for the L-subshell photoionization is found to be good at small photon ene rgies but it underestimates the cross sections at large photon energie s.