Quasi-Resonance charge transfer

Finally in this section, we note that the use of perturbation theory, particularly for quasi-resonant charge transfer, has been developed by Battaglia, George and Lanaro They show that first-order perturbation theory is satisfactory for high-velocity atoms, with Eq lying outside the solid band, and they have examined in detail protons scattered from alkali-halide... 

Quasi-resonance charge transfer will accompany resonance charge transfer if a core hole exists within the departing atomic emission of the substrate. For this to occur, a significant amount of energy must be imparted during the atomic collisions in knock-on sputtering. When present, an additional channel for electron transfer... 

Quasi-resonance charge transfer An electron transfer process resulting in secondary ion formation or neutralization... 

Figure 3.25 Potential energy diagrams representative of (a) resonant charge transfer (RI = Resonant Ionization of a neutral atom and RN = Resonant Neutralization of a positive ion), (b) Qnasi-resonant charge transfer (qRN = quasi-Resonant Neutralization of a positive ion) and Auger charge transfer (AN-Auger Neutralization of a positive ion). The dashed arrows represent electron transfer from populated to vacant electron levels, whereas the horizontal lines represent the allowed electron levels, otherwise referred to as stationary states.

Nevertheless, the one-electron approach does have its deHciencies, and we believe that a major theoretical effort must now be devoted to improving on it. This is not only in order to obtain better quantitative results but, perhaps more importantly, to develop a framework which can encompass all types of charge-transfer processes, including Auger and quasi-resonant ones. To do so is likely to require the use of many-electron multi-configurational wavefunctions. There have been some attempts along these lines and we have indicated, in detail, how such a theory might be developed. The few many-electron calculations which have been made do differ qualitatively from the one-electron results for the same systems and, clearly, further calculations on other systems are required. 

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