Rayleigh near-resonant

J. L. Carlsten and A. Szoke. Spectral resolution of near-resonant Rayleigh scattering and collision induced resonance fluorescence. Phys. Rev. Lett., 56 667-671 (1976). 

Figure 17.2.7 Schematic views of Raman scattering. Excitation (E) to a nonstationary virtual state is followed by Rayleigh scattering (R ) with no change in energy, or Raman scattering (R and R2) with energy changes equal to vibrational quanta, (a) The normal Raman effect involves excitation in a nonabsorbing region, (b) The resonance Raman effect involves excitation very near an allowed absorption transition.

These three salts are isobaric because the masses of the anions and cations are nearly the same. Although crossing resonances were somewhat unexpectedly observed in the studies of KBr and to a lesser extent in Rbl, for these compounds an Sg mode, the folded extension of the Rayleigh wave as in Fig. 6, was anticipated [70]. For the isobaric case, this vibration appears to be a tme surface mode at least for part of the way across the SBZ and not just a resonance with a high density of states at the surface [70],... 

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