Spin-flip Raman processes

Resonance Raman and antisymmetric scattering are involved in a novel technique involving spin-flip Raman transitions in paramagnetic molecules that can function as Raman electron paramagnetic resonance. Figure 3.2a shows a conventional vibrational Stokes resonance Raman process, while 3.2b and 3.2c show the polarization characteristics of the two distinct spin-flip Raman processes for scattering at 90°... 

Fig. 6. Diagram of the two-magnon Raman scattering process in the cuprates (a) initial antiferromagnetic spin configuration on the Cu sites (b) incident photon excitation of a spin-up Cu(3d ) hole to an intermediate-state 0(2p) orbital (c) double spin flip due to direct spin exchange between the spin-up hole on the intermediate-state 0(2p) site and a spin-down hole on a nearest-neighbor Cu site (d) hopping of a spin-down hole from the 0(2p) intermediate state to the original copper site, emitting the scattered photon.

On the basis of the experimental data presented above, one cjin exclude on the onset several models for the "blue peak" emission. Firstly, spin-flip collision induced population inversion on the Di transition is not involved - due to both the off-resonant character of the emission and its independence on the buffer gas pressure. Similarly, pressure induced extra resonances are rejected. Stimulated electronic Raman and three photon scattering effects, both by a two or three level system, are dependent on the laser detuning and neither their frequencies are to the blue in the vicinity of the Di line (figure 2) thus, these processes are also excluded. 

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