Multiple Ionization of Atoms

Abstract

Spectroscopic data of atoms and atomic ions show that the binding energy significantly exceeds the atomic ionization potential for an electron in a singly charged ion (and even more so in a multiply charged ion). It is approximately twice as high for alkaline-earth atoms and atoms of noble gases, and over five times as high for the alkali atoms. The energy required for the production of a multiply charged ion is approximately equal to the sum of binding energies of electrons in an atom and in ions under stepwise ionization. For this reason it had long been assumed that the possibility of multiple nonlinear ionization of atoms at radiation field strengths less than the atomic field strength is negligible.