Excitation transfer resonance

LaMorte, Y. J., Zoumi, A. and Tromberg, B. J. (2003). Spectroscopic approach for monitoring two-photon excited fluorescence resonance energy transfer from homodimers at the subcellular level. J. Biomed. Opt. 8, 357-61. 

Thus, it is concluded that the de-excitation of the metastable Ar( P2 and Pq) atoms is ascribed to the nonadiabatic excitation transfer at large intermolecular distance by the crossing of the intermolecular potential curves between the initial Ar -M channel and the final Ar-M channel, and the de-excitation of the resonant Ar( Pi and Pi) to the resonant excitation transfer by the dipole-dipole interaction [153]. This conclusion is compatible with the result of the above-mentioned conclusions for the de-excitation of He(2 P) by Ne [135]. 

Radiationless excitation transfer occurs only when (D + A) initial state is in or near resonance with (D +A ) final state and there is a suitable donor-acceptor interaction between them. The rate of transfer, kt> a. is given by the time-dependent perturbation theory,... 

The interactions between metastable noble-gas atoms and ground-state noble-gas atoms are relatively simple and have been investigated quite extensively. If the excitation energy is lower than the ionization potential of the collision partner, the only important inelastic process is the transfer of excitation energy.12 The excitation transfer is usually very efficient when the process is near resonant. The process that is responsible for the operation of the He-Ne laser,13... 

The electronic coupling between an initial (reactant) and a final (product) state plays a key role in many interesting chemical and biochemical photoinduced energy and electron transfer reactions. In excitation (or resonance) energy transfers (EET or RET) [1,2], the excitation energy from a donor system in an electronic excited state (D ) is transferred to a sensitizer (or acceptor) system (A). Alternatively, in photoinduced electron transfers (ET) [3,4], a donor (D) transfers an electron to an acceptor (A) after photoexcitation of one of the components (see Figure 3.50). 

R. S. Knox and H. van Amerongen., Refractive index dependence of the Forster resonance excitation transfer rate, J. Phys. Chem. B, 106 (2002) 5289-5293. 

R. D. Harcourt, G. D. Scholes and K. P. Ghiggino, Rate expressions for excitation transfer. II. Electronic considerations of direct and through-configuration exciton resonance interactions, J. Chem. Phys., 101 (1994) 10521-10525. 

Several theories have been developed to explain how energy absorbed by one molecule is transferred to a second acceptor molecule of the same or a different species. At first sight exciton theory,20 66 which accounts for excitation transfer in molecular aggregates or crystals and the Davydov splitting effects connected with it, appears to bear little relationship to the treatment of long-range resonance transfer as developed, for example, by Forster.81-32 However, these theories can be shown to arise from the same general considerations treated at different well-defined mathematical limits.33-79... 

Optical excitation transfer can occur between molecules as much as 10 nm apart when the dipole-dipole coupling between molecules (one excited "photon donor" chromophore, the other an unexcited "photon acceptor" chromophore) by a mechanism known as Forster79 resonance transfer or fluorescence resonance energy transfer (FRET) its characteristic dependence on the distance r between the two chromophores is r 6. 

Most, though not all, studies of collisional excitation transfer in alkali atoms have dealt with the 2P1/2 and 2Pa/i resonance substates. The experimental procedure usually involves the excitation of one 2P fine-structure state... 

Frish and Kraulinya and, most recently, by Czajkowski, Skardis, and Krause [71] and Czajkowski, Krause and Skardis [96]. Frish and Bochkova [97, 98] studied excitation transfer from the 6 aPr and 6 aP0 mercury atoms excited by collisions with electrons in a discharge, to various states in sodium. Kraulinya [99] optically excited the Hg(6 aPJ state and followed the excitation transfer to sodium by monitoring the intensities of the collisionally sensitized sodium lines. Her results which are quoted within 30% — 50% are summarized in Table 4.5 and are compared with the cross sections determined by Czajkowski, Skardis and Krause [71], The considerable discrepancies between the two sets of results are apparently due to errors arising from the trapping of mercury resonance radiation [100, 28] which must have particularly affected Kraulinya s results, and from the uncertainty in the determination of the mercury and sodium vapor densities in the binary mixture. 

On the other hand, the results of more recent studies by Cheron [111] and by Czajkowski and Krause [101] who investigated Hg(6 aP ) -> Cd(5 aP excitation transfer and obtained a cross section of 4.6 x 10 A, suggest that the transfer proceeds by ordinary 2-body collisions. Czajkowski s cross section, which is considerably smaller than Morozov s and Kraulinya s values, lies well on the general resonance curve shown in Fig. 4.9, together with other similar cross sections for excitation transfer between dissimilar partners. 

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