Formation of electronically excited states

Photophysical processes involved in the photodegradation and photoinitiated degradation are  

Absorption in which electronically excited singlet (S) states are formed. 

Radiationless transition (intersystem crossing, ISC), which allows the formation of the electronically excited triplet (T) state. 

Formation of free radicals from excited singlet (S) and/or triplet (T) states. 

Energy transfer processes between and excited donor (D) and acceptor A) molecules (cf. section 1.4). 

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In the context of an introduction to organic aspects of photochemistry, a simple molecular orbital description of the electronic structure of organic molecules provides the most convenient qualitative framework in which to discuss the formation of electronically excited states by the absorption of light. It is normally assumed that the inner-shell electrons of the constituent atoms of a molecule remain unaltered in the molecule itself linear combinations of the remaining, va lence-shell atomic orbitals then provide molecular orbitals that can be used to describe the outer electronic structure in the molecule. 

The irradiation of pure water with high-energy electrons generated by an accelerator results in the rapid formation of electronically excited states and/ or free radicals in 10-14 to 10 9 s. These reactive species will react with organic... 

Photoelectron ejection is for some molecules connected with the reaction of a solvated electron with other species, as it is known that in several cases this reaction leads to the formation of electronically excited states [Eq. (99)]. Whether reaction (99) or (100) prevails, when reaction (100) is very exoergonic, is of course important for a discussion of Marcus or anti-Marcus behavior (Section 6). 

To understand how pollutants are decomposed by ionizing radiation, it is necessary to review aqueous-based radiation chemistry. The irradiation of water results in the formation of electronically excited states, free radicals and ions along the path (spur) of the incident particle. The reactive species... 

In both cases, of course, the involvement of light takes place via the formation of electronically excited states. 

The absorption of photons by molecular oxygen and the chromophores in the resist polymers, leading to the formation of electronically excited states of oxygen species and chromophoric groups of the polymer, respectively. 

The large class of hetero-atom combination reactions has not been at all fully investigated. Examples of such reactions which lead to the formation of electronically excited states as detected in discharge-flow systems are ... 

The formation of electronically excited states of Og by physical quenching of exdted states of sensitizers was originally suggested by Kautsky (90) and more recently by Sharp (97). Kautsky, studyring... 

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