Iron oxide excited state lifetime

State lifetimes and modes of energy transfer within the structure. Examples of this are photoluminescence of ZnS nanoparticles studied by Wu et al. (1994), and Mn doped ZnS nanoparticles by Bhargava et al. (1994). In the latter study, the doped nanocrystals were found to have higher quantum efficiency for fluorescence emission than bulk material, and a substantially smaller excited state lifetime. In the case of environmental nanoparticles of iron and manganese oxides, photoluminescence due to any activator dopant would be quenched by magnetic coupling and lattice vibrations. This reduces the utility of photoluminescence studies to excited state lifetimes due to particle-dopant coupling of various types. The fluorescence of uranyl ion sorbed onto iron oxides has been studied in this way, but not as a function of particle size. 

Chemiluminescence and photoluminescence in diatomic iron oxide, Rb2, and alkali-metal dimers with halogen atoms and metal vapour-oxidant flames,202 203 lifetime measurements of selectively excited states of diatomic hydrides,204 photodissociation of alkali-metal halide vapours,206 spin-orbit relaxation of the HTe ( 2IIi) radical,20 the photodecomposition of metal carbonyl anions such as [Mn(C04)] in the vapour phase,207 and the fluorescence of Rhodamine 6G in the vapour phase 208 have been studied in recent reports. In the last study it was concluded that an insufficient concentration of the fluorescing dye could be maintained in the vapour phase to permit laser action to occur. 

The above discussions may be summarized as follows when the acceptor side of the reaction center is oxidized, i.e., it is in the [Pd] QA-state, light activation produces the P -state, i.e., the [P" -r]-Q -state, where I is the transient intermediary electron acceptor, namely a BO molecule. When the reaction center is pre-reduced to the [Pdj QA -state, light activation produces the P -state, i.e., the [ P-l]-Q -state with a lifetime of 10 ns. Most of the radical pairs recombine to reform the original [P-I] state, but some form the triplet state of P. In the initial excited singlet state [P 4 ], the spins on and r are antiparallel. During the 10-n lifetime of the excited singlet state, the spins of the unpaired electrons on the radical pair interact with nuclear spins on the two molecules, or with the electron spins on or the nonheme iron atom, but in any case there is a rephasing of these two unpaired spins. Recombination of these radical pairs, now with a predominantly triplet character, leads to the formation of the triplet state of P, i.e., theP -state [P -r] QA" [P -H-Qa" -> Pdl-QA. ... 

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