Abstract
In order to provide a general background for the following discussions on the localizability and motion of electronic excitation, we attempt to review some of the basic concepts related to excitons in molecular crystals [1–7]. One of our purposes is to define rigorously, in the limit of a weak matter-radiation interaction, the light absorbing entities and the subsequent processes of electronic excitation energy transformation. We know that individual molecules can only be taken as the light absorbing entities under very special conditions, which must be discussed in each case.
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References
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These modes may be seen in the following way: a molecular excitation to level lnn> may be represented by an electronic oscillator μon exp [i(En-En)t/h], where μon is a matrix element of an electronic dipole operator. The resonant electronic oscillators, associated with each site, couple weakly and form modes of electronic oscillations: μok exp [i(E k -E o )t/h].
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Note however that this crossed relaxation term disappears by symmetry for the dimers. (Cl. Aslangul, private communication).
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Voltz, R., Kottis, P. (1976). Excitons and Electronic Collective Excitations in Molecular Organic Solids. In: Chalvet, O., Daudel, R., Diner, S., Malrieu, J.P. (eds) Localization and Delocalization in Quantum Chemistry. Localization and Delocalization in Quantum Chemistry, vol 2. Springer, Dordrecht. https://doi.org/10.1007/978-94-010-1456-4_11
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