Exchange Interaction Contributions

Here pW(ri,R), (n,/ ) and q) - r2,R),(p r2,R), are asymptotic wave functions of the first and of the second electrons located near corresponding atom cores. Equations (3.1.18) and (3.1.19) are written in the molecular coordinate system in which the interacting atoms are located on the axis z, and the center of the interatomic separation is taken as the origin of coordinates. In this coordinate system ri and r2 are the coordinates of the first and of the second electrons. The functions Xi r, r2,R) and Xiii i f2,R) accounting the interaction of electrons with each other and with extraneous nuclei have complicated forms and are given in [12]. 

The function (p r,R) can be obtained from the asymptotic radial wave function of a valence electron of a neutral atom. This radial wave in the coordinate system with the origin in the atom nuclear has the form [11]  

Then the exchange interaction contribution into a-component of the dipole moment for two interacting atoms may be represented as [13] 

The results obtained for atoms with the valence s-electrons can also be applied, after minimal changes, to interacting atoms having the valence electrons of nonzero orbital moment 1. Indeed, the exchange interaction occurs in the range of electron coordinates near the axis z where the angular wave functions of the electrons vary 

---

More related to general photochemistry are the papers which have appeared on wholly or partly diffusion-controlled reactions. The effect of a very short lifetime of the donor on the calculation of fluorescence quantum yields and lifetimes has been analysed by Viriot et al. Andre et al. analyse the kinetics of energy transfer to an acceptor when there are two different excited states capable of acting as donors and when interaction between these states is possible. The exchange interaction contribution to energy transfer between ions in the rapid diffusion limit... 

In general, for ET processes associated to allowed transitions (usually singlet-singlet), both dipole-dipole (Coulombic) and the exchange interactions are involved. In the case of forbidden transitions, only exchange interaction contributes to the observed ET process. The dependence on the distance of the rates of the two process is anyway rather different the rate of dipole-dipole-induced ET decreases as R, whereas that of the exchange-induced process decreases as exp(—2/ /L). 

The dominating contribution to exchange interaction is isotropic as expressed by the scalar parameter used in (4.80) anisotropic and antisymmetric contributions [87] are mostly ignored. Equation (4.80) can be evaluated in the coupled presenta-... 

Finally, we discuss the effects of chalcogen (S to Se) substitution. Although in (EDS-TTF)2FeBr4 remarkably close Se---Br contacts exist between donor and anion layers, little magnetic exchange interaction exists between the magnetic anions. The molecular orbital calculation reveals that the contribution of Se 4p orbital to the HOMO of the EDS-TTF molecule is considerably smaller than the contribution of... 

---