Exciton annihilation – a physical process and a spectroscopic tool

This project is related to the following Fields, Subjects and Techniques:

In case of high excitation intensities it may happen that two nearby molecules both are excited. Now it may happen that one excitation is transferred onto already excited molecule creating higher excited state Sn followed by a rapid internal conversion back to the first excited state. The result of the process is that one excitation gets lost - it is annihilated. If the interaction between the molecules is strong, one should think in terms of exciton states. In this terminology the situation with two excitations corresponds to so called two-exciton states. Now, the different exciton manifolds (one-exciton, two-exciton, etc.) are coupled via mixing with the molecular multiply-excited states Sn and the related internal conversion. We have successfully used both molecular and excitonic descriptions of annihilation to describe intensity-dependent kinetics in various systems like antenna complexes, conjugated polymers and artificial antenna complexes. Complimented with transmission electron microscopy, the annihilation studies enabled to obtain detailed nano-scale information about conditions of forming different aggregation phases of ternary protein-surfactant-water system. We have extended this work to low temperatures where the multiexcitonic annihilation model was used and further developed to describe the temperature dependence of annihilation.