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Theory of the energy levels of donor-acceptor pairs

1960; Elsevier BV; Volume: 12; Issue: 3-4 Linguagem: Inglês

10.1016/0022-3697(60)90048-2

1879-2553

Ferd E. Williams,

Molecular Junctions and Nanostructures

The electronic energy levels of the donor-acceptor pair are investigated theoretically in the effective mass approximation in a way similar to the Heitler-London treatment of the hydrogen molecule. The cores are approximated by point charges; the medium, by a continuous dielectric; and the two-particle wave function, by a single product of the separated donor and acceptor wave functions. No exchange integral arises, and the total ionization energy decreases with increasing degree of association. The analysis is generalized to pairs whose electron and hole masses are unequal and to pairs in polar media. The optical transition energies involved in the creation and evolved in the annihilation of the bound exciton are calculated. The effect of state of ionization on the electron and hole levels is determined. In highly-associated pairs the ionization of the electron or hole greatly reduces the ionization energy of the remaining particle. The analysis is applied to zinc sulfide containing Group IIIB donors and Group IB acceptors, and supports the identification of the long-wavelength luminescent emission as the transition between the ground states of donor and acceptor in quite highly-associated pairs. Other possible applications are suggested.