Page - 67 - in Advanced Chemical Kinetics

product is thekey toperformanykindof reaction control and to choose all the experimental conditions that satisfy the reaction requirements. The rate constants, the intermediate forma- tion and structures, the reasons for interconversions, energy migrations and excited states deactivationarecrucial toexertanysortofreactioncontrol.For that, thekinetic lawsofexcited state intermediate formation, thecharacteristicsof funnelsandthedifferencebetweenthermal andphoto-activated chemical reactions and thekinetics involved inenergy transferprocesses mustbe scrutinized.As showedbySobolevaet al. [5], todescribe the electronic excited states lifetimes isvery important toevenproposemechanisms for charge transfer in supramolecular systems. In theirwork, they showed that electron transfer kinetics canbemonitoredby time- resolved luminescence quenching measurements of a chromophore in the presence of a quencher todescribe the electron-transfer reactivity in sodiumdodecyl sulfate (SDS)micellar systems. They observed that themobility of the quencher is faster than the electron-transfer rate,whichresulted in theconclusion that, in thecaseswhereelectron transferbetweendonor and acceptor is slower than the diffusion rate, the transfer is then controlled by reaction kinetics insteadofbydiffusion. All these phenomenaoccur in a systemof competitionvs. cooperation, through intermediates andgovernedbyprobabilities of occurrence and rate constants, as theydirect themechanisms thatareemployedinagreatnumberofapplications.Examplesareprobinginimagingdiagnosis, energyconversionandstorage,datastorage,photodynamic therapy,amongseveralothers. 6.State-of-the-art Nowadays, photophysical and photochemical processes are perceptively and actively being applied in several areasof science and technology topromotea rapidandsustainableway to Figure 7. Potential curves of ground and electronic excited states of a photochemical reaction. (R) is the ground state reactant, (*R) is theexcitedreactant, (I) is thegroundstate intermediateofa reaction, (*I) is theexcitedstate intermediate, (*P) is theexcitedstateproductand(P) is the finalproductof theoverallprocess. New Materials to Solve Energy Issues through Photochemical and Photophysical Processes: The Kinetics Involved http://dx.doi.org/10.5772/intechopen.70467 67