Exciton fusion

Klymko, P. and Kopelman, R., Fractal reaction-kinetics Exciton fusion on clusters, Journal of Physical Chemistry, Vol. 87, No. 23, 1983,... 

The singlet-singlet collision process is often referred to as singlet exciton fusion. The end result of such a fusion reaction... 

This kinetic analysis of the singlet exciton fusion process is provided by the equation... 

The fusion of two triplets may give rise to autoionization as observed in the case of singlet exciton fusion (67)... 

Time dependent fluorescence depolarization is influenced by the exciton annihilation which occurs in confined molecular domains . Photoemission results from singlet exciton fusion as shown by the excitation intensity dependence which occurs in anthracene crystals. Reabsorption of excitonic luminescence is an effect which has been shown to occur in pyrene crystals. The dynamics of exciton trapping in p-methylnaphthalene doped naphthalene crystals involves phonon assisted detrapping of electronic energy. Ps time resolved spectroscopy was the experimental technique used in this work. 

Lately it was found, that the same mechanism is realized also in bacteria41 b. Exciton fusion processes observed by excitation of photosynthesis with very intensive ps- or ns-flashes41c,d practically do not occur under natural excitation conditions (s. Ref.41b ). 

It is a competing process to Si So emission and is partly responsible for the the low fluorescence quantum yield from crystalline tetracene. Fission is also a biex-citonic process, which, like triplet exciton fusion, can be modulated by an applied magnetic field with a similar dependence as shown in Fig. 6.24 for fusion (see also Fig. 6.26). The fluorescence intensity of tetracene is therefore magnetic-field dependent [51]. 

Klymko, P. W. Kopelman, R. Fractal reaction kinetics exciton fusion on clusters. I Phys. Chem. 1983, 87(23), 4565-4567. 

A semiquantitative model of the effects of L on Ip>F rid Ip was given by Webber and Swenberg (11). These authors analyzed the dependence of exciton annihilation on parameters such as lattice size, lattice dimensionality and the exciton fusion rate using a Pauli-Master equation. Their treatment is quite similar to the formalism of Paillotin et (12) used in modeling the fluorescence quantum yield decreases observed in photosynthetic membranes (13) with increasing excitation... 

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