Threshold of Photoionization into a Vacuum

If VQ 0, then the threshold for photoionization into a vacuum Eva( = -Ee(ls). If VQ 0, then that additional energy has to be supplied. Delahay (1976) has summarized this process, but the actual mechanism is still debatable. If AH and Evac are experimentally known, one can get an experimental measure of the medium rearrangement energy in the ground state, EM(ls) = E - AH. On that basis, since EM is always positive, Kestner (1976) prefers the lower experimental value of AH for e.  

In many respects, the FFK formulation is similar to that of CKJ. The differences are the following  

The hard-core radius of the solvent molecules is absent in FFK. 

TABLE 6.5 Results of Calculations Using the FFK Semicontinuum Model  

Kevan (1974) and Tachiya (1972) point out that CKJ use an SCF approximation to calculate the medium polarization energy, but in everything else they use the adiabatic approximation. This somewhat inconsistent procedure, which may be called the modified adiabatic approximation, gives results similar to those obtained by FFK. Varying the dipole moment and the polarizability in the semicontinuum models varies the result qualitatively in the same direction. It increases the electron-solvent attraction in the first shell and also increases the dipole-dipole repulsion. Both hv and I increase with the dipole moment, but not proportionately. 

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