Back ionization wave

In reverse, these processes liberate the equivalent amount of energy, mostly as heat. Ionized particles are responsible for the reflection of radio waves back toward Earth. 

Fig. 13. Schematic view of the irradiated STIRAP process (Stimulated Raman pumping) (a) The chirped pump pulse excites the system the electronic ground state (b) the system is stimulated back down to the electronic ground state, but a Stokes-shifted higher vibrational level, (c) The resulting wave packet is probed by the delayed probe pulse, which ionizes the particle from the oscillating ground state.

The final state has p symmetry as imposed by the dipole selection rule A/ = 1. This eases the extrapolation of calculated just outside the ionized atom represented by a muffin-tin potential, to near its nucleus, thus obtaining the result of the interference of the outgoing wave with the waves scattered back from the surrounding neutral atoms represented by 6-function potentials. When the waves add constructively, o increases and vice-versa. 

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