Energy continued singlet

The total set of resonant sublevels participating in the RLT typically consists of a small number of active acceptor modes with nonzero matrix elements (2.59) and many inactive modes with Fi( = 0. The latter play the role of the reservoir and ensure the resonance condition Et = Ef. For aromatic hydrocarbon molecules, for example, the main acceptor modes are strongly anharmonic C-H vibrations that accept most of the electronic energy in singlet-triplet transitions. The inactive modes in this case are the stretching and bending vibrations of the carbon skeleton. The value of p( afforded by these intramolecular vibrations is often so large that they behave as an essentially continuous bath even in the absence of intermolecular vibrations. This statement is supported by the observation that RLT rates for many molecules embedded in crystal lattices are similar to those of the isolated gas-phase molecules. 

There is a degree in the continuity and discontinuity of the orbital phase [20]. 2-Oxopropane-l,3-diyl (Scheme 10) is a hetero analog of trimethylenemethane (TMM) where the orbital phase is continuous in the triplet diradical (Sect. 2.1.5) and discontinuous in the singlet diradical (Sect. 2.1.6). The n and orbitals of carbonyl bonds are lower in energy than those of C=C bonds. The lowering strengthens the interaction of the radical orbitals (a, b) with and weakens that... 

Fig. 1 The effect of size on metals. Whereas bulk metal and metal nanoparticles have a continuous band of energy levels, the limited number of atoms in metal clusters results in discrete energy levels, allowing interaction with light by electronic transitions between energy levels. Metal clusters bridge the gap between single atoms and nanoparticles. Even though in the figure the energy levels are denoted as singlets, we must remark that the spin state of the silver clusters is not yet firmly established...

Scheme 1 Major photochemical processes of coloured dissolved natural organic matter (CDOM) that may lead to the transformation of organic contaminants.1X1 Excited singlet state of the species X, 3X excited triplet state of the species X, P an organic contaminant, Pox oxidation product(s) formed upon reaction of P with singlet oxygen, full arrow heads chemical reactions, open arrow heads energy transfer/loss processes, continuous arrows radiative processes, dashed arrows radiationless processes...

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