Rayleigh scattering vs raman scattering

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Discussion Overview

The discussion focuses on the differences and similarities between Rayleigh scattering and Raman scattering, exploring their mechanisms, energy exchanges, and implications for phenomena such as the blue color of the sky. The scope includes theoretical explanations and conceptual clarifications regarding these scattering processes.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that both Rayleigh and Raman scattering are second-order processes, but differ in that Rayleigh scattering has the same final state as the initial state, while Raman scattering does not.
  • One participant suggests that the strength of Raman scattering should be much larger than Rayleigh scattering due to the presence of many final states.
  • Another participant emphasizes that Rayleigh scattering is elastic, meaning the incoming and scattered light wavelengths are the same, while Raman scattering is inelastic, resulting in energy loss.
  • It is mentioned that Raman scattering occurs at a much lower rate compared to Rayleigh scattering, with estimates suggesting only 1 in 10,000,000 photons undergo Raman scattering.
  • One participant questions the assertion that Raman scattering occurs at a slower rate than Rayleigh scattering, proposing that both effects may occur at the same rate but with different photon fluxes.
  • Another participant reiterates that Rayleigh scattering is more prevalent due to the larger number of photons involved, particularly when the scatterers are smaller than the wavelength of the incident light.

Areas of Agreement / Disagreement

Participants express differing views on the relative rates of Rayleigh and Raman scattering, with some asserting that Raman scattering is less frequent while others challenge this notion. There is no consensus on the implications of these scattering processes for the blue color of the sky.

Contextual Notes

Participants mention various assumptions regarding the conditions under which Rayleigh and Raman scattering occur, including the size of scatterers relative to the wavelength of light and the energy exchanges involved in each process. These factors remain unresolved in the discussion.

wdlang
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both rayleigh scattering and raman scattering are second order processes

the difference is only that the final state of the atom/molecule coindices with the initial state of the atom/molecule in rayleigh scattering, while in raman scattering, the final state is different from the initial state.

since there are many final states, the strength of the raman scattering should by much larger than rayleigh scattering, is not it?

Why people contribute the blue sky to rayleigh scattering but not raman scattering?
 
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Rayleigh..here no energy is lost. Incoming light's wave length and scattered light wave length will be same. This is very good at small wavelengths..
Raman...Here energy is lost (i.e., inelastic process). Very small (1 in 10000000 photon) will suffer Raman scattering. Remaining is Rayleigh scattering. Raman effect makes the molecules to rotate/excite. Also since this is very small and so one cannot say blue color of sky is due to Raman effect.
 
Last edited:
Rajini said:
Rayleigh..here no energy is lost. Incoming light's wave length and scattered light wave length will be same. This is very good at small wavelengths..
Raman...Here energy is lost (i.e., inelastic process). Very small (1 in 10000000 photon) will suffer Raman scattering. Remaining is Rayleigh scattering. Raman effect makes the molecules to rotate/excite. Also since this is very small and so one cannot say blue color of sky is due to Raman effect.

i do not think the rate of raman scattering is slow than rayleigh scattering

they are both second order processes
 
Rayleigh it is elastic (incoming and scattered light ray will have same energy) process and Raman is Inelastic (energy may be increased or decreased!) process!..This is what i want to say..May be both effect occur at same rate! But the flux (i mean more photons) is more in Rayleigh. For Rayleigh to occur the scatters should be small than wavelength of photon..
 

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