Rayleigh light-scattering

Figure 1.2. Raman spectrum of room-temperature chloroform obtained with 514.5 nm light. Rayleigh scattering at zero Raman shift is heavily attenuated by a band reject filter and is actually several orders of magnitude more intense than the Raman scattering. The x axis is shown in three different scales but is normally plotted as Raman shift in reciprocal centimeters relative to the laser frequency (19,435 cm in this case). Although the Stokes Raman to the right is actually a negative frequency shift, convention assigns Stokes Raman shifts as positive numbers.

The first term in equation (7) corresponds to the elastic component of the scattered light (Rayleigh scattering), while the second term corresponds to the inelastically scattered Raman component. Equation (7) also indicates that Raman scattered light can occur at two new frequencies different from the incident light frequency. These correspond to Stokes and anti-... 

When the particle diameter is less than 10% of the wavelength of light, Rayleigh scattering is observed, in which the efficiency factor is given by... 

Incident light Rayleigh scattering Raman scattering... 

The first temi results in Rayleigh scattering which is at the same frequency as the exciting radiation. The second temi describes Raman scattering. There will be scattered light at (Vq - and (Vq -i- v ), that is at sum and difference frequencies of the excitation field and the vibrational frequency. Since a. x is about a factor of 10 smaller than a, it is necessary to have a very efficient method for dispersing the scattered light. 

Thus Rg is a constant in any particular experiment where Rayleigh scattering is obtained, since the entire angular dependence of the light intensity is correctly contained in the 1 + cos 6 term. 

The Rayleigh scattering extinction coefficient for particle-free air is 0.012 km for "green" light (y = 0.05 /rm) at sea level (4). This permits a visual range of —320 km. The particle-free, or Rayleigh scattering, case represents the best visibility possible with the current atmosphere on earth. 

Fig. 10-5. Comparison of for 0.1 ppm NO2 and Rayleigh scattering by air. The photopic eye response represents the range of wavelengths over which the eye detects light. Source Husar, R., White, W. H., Paterson, D. E., and Trijonis, J., "Visibility Impairment in the Atmosphere," Draft report prepared for the U.S. Environmental Protection Agency under Contract No. 68022515, Task Order No. 28.

Rayleigh Scattering the scattering of light by particles much smaller than the wavelength of the light, e.g., molecular scattering in the natural atmosphere. 

Figure 24. The acquisition camera image of the Keck LGS with the segmented mirror "unstacked." The brightening on the left is the Rayleigh scatter of light from the laser. The 36 spots show an elongation increasing with distance from the laser source, which is left of the camera.

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