Reactions via upper states

An increasing number of processes occurring at a faster than diffusion rate are being revealed, while advanced experimental methods become available. Advanced studies have afforded a much greater detail of the time evolution of electron transfer and proton transfer processes, but also some isomerization reactions occur at a rate 

Diffusional transport Diffuse solvation dynamics Vibrational cooling 

Barrierless Bimolecular charge transfer proton transfer 

Intersystem crossing likewise may follow more complicated mechanisms. Generalizations such as that expressed by the El Sayed rules prohibiting S-T transitirm when both states were njt or nn have been reexamined, evidencing a new path for the Si(njr ) — Ti(njt ) transition [25]. In nitroaromatics, intersystem crossing occurs within 100 fs following the path Si(jtJt ) T3(mt ) appar- 

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