Relaxation shift

Usually, the most general nonspecific effects of dipole-orientational and electronic polarization of the medium are discussed, and the results of the theory of relaxational shifts developed under the approximation of a continuous dielectric medium may be used.(86 88) The shift of the frequency of the emitted light with time is a function of the dielectric constant e0, the refractive index n, and the relaxation time xR ... 

It should be noted that a number of experimental observations do not agree with the Bakhshiev-Mazurenko model (1) the time-dependent range of relaxational shifts of spectra is considerably wider than that described by Eq. (2.9), which may be associated with the existence of a distribution of relaxation times 89 94, (2) the bandwidth of the fluorescence spectrum varies significantly during relaxation(93) (3) substantial deviations from exponential... 

There are substantial difficulties in the interpretation of temperature-dependent shifts of protein spectra because of the thermal lability of proteins and the possibility of temperature-dependent conformational transitions. Low-temperature studies in aqueous solutions revealed that for many of the proteins investigated the observed shifts of the fluorescence spectra within narrow temperature ranges were probably the result of cooperative conformational transitions, and not of relaxational shifts/100 1 Spectral shifts have also been observed for proteins in glass-forming solvents, 01) but here there arise difficulties associated with the possible effects of viscous solvents on the protein dynamics. 

As molecular weight increases, the slow relaxations shift progressively to longer times while the fast relaxations remain essentially unchanged. 

This is because for j = k the diagrams in Figs. 18 c, k give identical contributions in the monopole approximation. The presence of an extra core hole will only give small higher order corrections to the relaxation shift. For j,k belonging to the same main shell, it is still a reasonable approximation to set... 

Finally, a comment regarding relativistic effects and the calculation of one-electron energies and monopole relaxation shifts. The most convenient way to obtain relativistic zlSCF one-electron energies is to use the Dirac-Fock-Slater (DFS) zlSCF values tabulated by Huang et al.82). These are very close (a few tenths of an eV) to DF JSCF, and the relativistic monopole relaxation shift is the given by... 

Fig. 22. Static and dynamic relaxation shifts in the range < Pd to Sm. The static, monopole relaxation shift df° (—) is a theoretical number (Eq. (45)). The Fermi sea correlation shift A (-----) is deduced by comparison with experimental 4d XPS spectra. The dynamic dipole relaxation shift J,P1 (-) is deduced by comparison with experimental 4p XPS spectra (Eq. (49)), Afl =...

It is quite clear that when the gCK process reaches its maximum strength, the resulting shift idfR becomes a good deal larger than the normal static monopole relaxation shifts) f°. 

In Pd the 4 p width is considerably larger than the shift which means that during the formation of the tidal wave, the energy loss ( friction") is dominant and a maximum relaxation shift is not very probable. However, this does of course not violate the picture of a 4p hole as a stable excitation in the sense that the total width is still much smaller than the core-hole binding energy. However, in order to observe the Weisskopf-Wigner limit of exponential decay one may have to go back to the elements around 42Mo. 

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