Autoionization

The autoionization is an effect that can occur with atoms or molecules when an excited state is higher than the ionization energy. This can occur when two or more electrons are excited at the same time. The transfer of the energy of the first to the second electron can lead to ionization.

Excitation of two electrons

If in an atom with two valence electrons (eg beryllium - 2s ) are both excited into higher states, we obtain the total excitation energy of the atom:

Where and are the energies of the individual excitations of the electrons and the changed by the excitation energy of interaction between the excited and the remaining electrons ( in the lower shells) is.

This doubly excited state can be compensated either by emission of two photons or by energy transfer from one to the other electron. Since the latter process, the energy conservation must apply, the energy transfer is iA only possible if a suitable condition for highly excited single-electron excitation exists. For discrete energy but this is very unlikely, and so the process can be observed only for energy, as for free electrons are not subject to discrete energy spectrum. If the total energy above the ionization energy of a singly excited electron, the transfer of energy can lead to the second electron for ionization, in which the electron leaves the atom leads to a positive ion with total charge.