Chapter 1 - Alternative Designations of Absolute Partial Cross Sections

Abstract

The spectral distribution of the absolute total photoionization cross section of an atom or molecule can be partitioned into absolute partial cross sections in a variety of ways. Here, the partition is made largely in terms of ionization from Hartree-Fock-like orbitals following Koopmans' theorem, primarily because of the availability of such experimental data over a broad energy range, made possible by the increased spectral output of modern synchrotrons, and the more sophisticated detection methods, including photoelectron, photoion (separately and in coincidence). Partial cross sections for atoms may involve multiple ionization, and for molecules, fragment ions. Deviations from independent particle behavior, especially by ionization from inner-valence orbitals, are recognized. Each of the foregoing methods is discussed in detail in the chapters that follow.