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Singlet fission
In the area of spectroscopy, singlet fission is a spin-allowed process whereby a singlet excited state converts to two triplet states. The phenomenon is observed in molecular crystals where the molecules are appropriately oriented such that one excited molecule can share energy with a neighboring ground state molecule. The process occurs on a picosecond timescale. The overall process is related to intersystem crossing whereby, in a single molecule, an excited singlet state converts to a lower energy excited triplet.
==History==
The process of singlet fission was first introduced to describe the photophysics of anthracene in 1965.〔 Singh, S.; Jones, W. J.; Siebrand, W.; Stoicheff, B. P.; Schneider, W. G. ''J. Chem. Phys.'' 1965, ''42'', 330. 〕 Early studies on the effect of the magnetic field on the fluorescence of crystalline tetracene solidified understanding of singlet fission in polyacenes.
Pentacene is a prominent candidate for singlet fission due to the energy of its triplet state being less than half the energy of S1, thus satisfying the requirement of S1 ≥ 2T1). Singlet fission in functionalized pentacene compounds has been observed experimentally. Intramolecular singlet fission in covalently linked pentacene dimers with yields as high as 156% has also been reported.
It has been suggested that singlet fission in organic photovoltaic materials has the potential to increase the efficiency of these devices. The detailed mechanism of the process is unknown. This area engages scientists in the fields of synthetic chemistry, theoretical chemistry, physics, engineering, and spectroscopy .
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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