Ground-state dynamics, bimolecular reactions

The rate of absorption (step i) can be expressed as the absorption intensity /abs (which depends on the concentration of the ground-state complex and the intensity of light used in excitation), while the rate of luminescence (step ii) and the rate of all the nonradiative decay paths (step iii) follow first-order rate laws that depend only on the concentration of the excited-state complex (nonradiative collisional quenching by solvent is not unimolecular, but follows first-order kinetics because of the large excess of solvent molecules). Dynamic quenching (step iv) results from an electron-transfer reaction during a collision between a quencher molecule and an excited-state complex. This bimolecular reaction has a... 

The reaction dynamics of few excited complexes are known however, the opportunities provided by pulsed lasers promise to make this research area one of major emphasis of mechanistic studies. Such methods are necessary because few transition-metal complexes exist as electronically excited states in RT solutions with lifetimes exceeding 1 fjis, and many are shorter lived. Several competing processes lead to ES decay nonra-diative deactivation to the ground state (GS), radiative deactivation (i.e., emission) to the GS, unimolecular reaction to products (such as ligand substitutions or redox decomposition) or bimolecular electron transfer or energy transfer with another species, Q, in solution. These processes are indicated in Eqs. (a)-(e) for a hypothetical complex [MLJ" + ... 

Among four-atom reactions this system has become a prototype test case for the comparison between quantum state resolved dynamics experiments and bimolecular collision theory. In 1973 the first semi-empirical LEPS and BEBO PESs were constructed by Zellner and Smith [56]. The subsequent development of a global H-HOH(A ground state PES in 1980 [20b], based on ab initio calculations [20ak was favoured by the fact that three of the four atoms involved are H atoms. The... 

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