Raman effect stimulated scattering

Here, E is the strength of the applied electric field (laser beam), a the polarizability and / and y the first and second hyper-polarizabilities, respectively. In the case of conventional Raman spectroscopy with CW lasers (E, 104 V cm-1), the contributions of the / and y terms to P are insignificant since a fi y. Their contributions become significant, however, when the sample is irradiated with extremely strong laser pulses ( 109 V cm-1) created by Q-switched ruby or Nd-YAG lasers (10-100 MW peak power). These giant pulses lead to novel spectroscopic phenomena such as the hyper-Raman effect, stimulated Raman effect, inverse Raman effect, coherent anti-Stokes Raman scattering (CARS), and photoacoustic Raman spectroscopy (PARS). Figure 3-40 shows transition schemes involved in each type of nonlinear Raman spectroscopy. (See Refs. 104-110.)... 

In the stimulated Raman effect it is only the vibration that gives the most intense Raman scattering that is involved this is the case for Vj in benzene. 

High-power pulsed lasers offer the possibility of studying nonlinear phenomena such as stimulated Raman scattering, the inverse Raman effect and the hyper-Raman effect. These investigations have contributed much to our knowledge of the solid-state and liquid stucture of matter and its higher order constants. 

Another extremely well-represented group of experiments were those exploiting the Raman effect (29-35). Interestingly, in addition to the four experiments in this group involving simple Raman scattering (29-32), three involved nonlinear Raman effects. These included stimulated Raman scattering (33, 34), and surface enhanced Raman (35). These Raman experiments can be found listed in Table III. 

When the power of the exciting radiation is raised into the megawatt range, nonlinear Raman effects are observed, namely the stimulated Raman effect, the inverse Raman effect (Stoicheff absorption), and the hyper-Raman effect. The results of such experiments with single crystals will be discussed in the last chapter, with special emphasis on stimulated Raman scattering from polaritons. 

Nonlinear Raman processes 163 Spontaneous scattering hyper Raman effect 163 Stimulated Raman effect 164... 

The most venerable of the nonlinear Raman effects is stimulated Raman scattering, first observed by Woodbury and Ng in 1962. The basic... 

To conclude this section we address the phenomenon of the stimulated Raman effect and its application to molecular spectroscopy. Stimulated Raman scattering is experimentally different from normal Raman scattering, in that it is observed in the forward direction (the stimulated Raman photon emerges into a very narrow cone to the propagation direction of the laser beam propagation direction). But the effect is normally only observed for high-power laser radiation. 

For a long time, as long as only one (giant-pulse) laser was used for excitation, the stimulated Raman effect [74] generated only the lines with the highest peak-scattering... 

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