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Directed energy transfer

Now let us consider tire implications of tliese results for energy transfer. First we recognize tliat tliere is no directed energy transfer of tire fonn considered in the incoherent case. Molecules in tire dimer cannot be recognized as well defined separate entities tliat can capture and translate excitation from one to anotlier. The captured excitation belongs to tire dimer, in otlier words, it is shared by botli molecules. The only counteriDart to energy migration... [Pg.3025]

As the pressure increases from low values, the pressure-dependent term in the denominator of Eq. (101) becomes significant, and the heat transfer is reduced from what is predicted from the free molecular flow heat transfer equation. Physically, this reduction in heat flow is a result of gas-gas collisions interfering with direct energy transfer between the gas molecules and the surfaces. If we use the heat conductivity parameters for water vapor and assume that the energy accommodation coefficient is unity, (aA0/X)dP — 150 I d cm- Thus, at a typical pressure for freeze drying of 0.1 torr, this term is unity at d 0.7 mm. Thus, gas-gas collisions reduce free molecular flow heat transfer by at least a factor of 2 for surfaces separated by less than 1 mm. Most heat transfer processes in freeze drying involve separation distances of at least a few tenths of a millimeter, so transition flow heat transfer is the most important mode of heat transfer through the gas. [Pg.678]

Zenkevich RAN, El NNA, Tomin VI (1982) Directed energy transfer due to orientational broadening of energy levels in photosynthetic pigments solutions. J Lumin 26 367-376... [Pg.221]

Nemkovich NA, Rubinov AN, Tomin VI (1980) Directed energy transfer in rigid single component solutions. JTP Lett 6 270-273... [Pg.222]

Fig. 9.4. Inhomogeneous spectral broadening responsible for directed energy transfer. The spectral overlap between the emission spectrum Eo of an excited species (whose absorption spectrum is Ao) and the absorption spectrum A2 of a solvate absorbing at higher... Fig. 9.4. Inhomogeneous spectral broadening responsible for directed energy transfer. The spectral overlap between the emission spectrum Eo of an excited species (whose absorption spectrum is Ao) and the absorption spectrum A2 of a solvate absorbing at higher...
Kiaeter J. and Blumen A. (1985) Direct Energy Transfer in Restricted Geometries,... [Pg.272]

Levitz P., Drake J. M. and Kiafter J. (1988) Critical Evaluation of the Applications of Direct Energy Transfer in Probing the Morphology of Porous Solids, J. Chem. Phys. 89, 5224-5236. [Pg.272]

Another class of red dopants, tetraphenylporphyrins (63), offer a direct energy transfer from blue to red [151], The absorption bands comprise the sharp porphyrin Soret band at 418 nm and the weaker Q bands at 512 and 550 nm. The photoluminescence shows two sharp transitions at 653 and 714 nm and can be induced from a blue emitting host by Forster transfer to the Soret band and internal conversion to the Q bands. [Pg.131]

Several dyes have been found to sensitize the cationic polymerization of cyclohexene oxide, epichlorohydrin, and 2-chloroethyl vinyl ether initiated by diaryliodonium salts (109,110). Acridinium dyes such as acridine orange and acridine yellow were found to be effective sensitizers. One example of a benzothiazolium dye (setoflavin T) was also reported, but no other class of dye nor any other example of a dye absorbing at longer wavelengths were discovered. Crivello and Lam favored a sensitization mechanism in which direct energy transfer from the dye to the diaryliodonium salt occurred. Pappas (12,106) provided evidence that both energy transfer and electron transfer sensitization were feasible in this system. [Pg.479]

Figure 24. Schematic representation of the proposed radiative and nonradiative processes occurring in nanocrystalline Mn2+ CdS. The straight lines represent radiative processes and the curved lines represent nonradiative processes. (1) Absorption to generate excitonic excited state. (2) Energy transfer to defect. (3) Energy transfer to Mn2+ via defect. (4) Radiative decay of defect. (5) Radiative decay of Mn2+. (6) Direct energy transfer to Mn2+. [Adapted from (122).]... Figure 24. Schematic representation of the proposed radiative and nonradiative processes occurring in nanocrystalline Mn2+ CdS. The straight lines represent radiative processes and the curved lines represent nonradiative processes. (1) Absorption to generate excitonic excited state. (2) Energy transfer to defect. (3) Energy transfer to Mn2+ via defect. (4) Radiative decay of defect. (5) Radiative decay of Mn2+. (6) Direct energy transfer to Mn2+. [Adapted from (122).]...
Fig. 91. Tetrametallic complex exhibiting Rn -to-Ln (Ln = Nd, Yb) directional energy transfer (Guo et al., 2004). Fig. 91. Tetrametallic complex exhibiting Rn -to-Ln (Ln = Nd, Yb) directional energy transfer (Guo et al., 2004).
Excitation of the Lnm ion by a d-transition metal ion is an alternative to chromophore-substituted ligands, and proof of principle has been demonstrated for several systems. The lack of quantitative data, however does not allow an evaluation of their real potential, except for their main advantage, which is the control of the luminescent properties of the 4f-metal ion by directional energy transfer. In this context, we note the emergence of self-assembly processes to build new edifices, particularly bi-metallic edifices, by the simultaneous recognition of two metal ions. This relatively unexplored area has already resulted in the design of edifices in which the rate of population, and therefore the apparent lifetime, of a 4f-excited state can be fine-tuned by energy transfer from a d-transition metal ion (Torelli et al., 2005). [Pg.455]

Mehlstaubl, M., Kottas, G.S., Colella, S., and De Cola, L. (2008) Sensitized near-infrared emission from ytter-bium(III) via direct energy transfer from iridium(III) in a heterometallic neutral complex. Dalton Transactions, 2385. [Pg.526]


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See also in sourсe #XX -- [ Pg.118 ]




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