I have a situation where I have an organic dye in aqueous solution, through which I have sent a (green) laser beam and measured the intensity. Compared to pure water, this solution showed much greater attenuation.

My question is then, is this enough evidence to conclude that absorption of photons by the dye molecules (electron transitions) predominates over scattering as a source of attenuation? From what I have been able to find out, scattering is relevant only for situations where particle size << $\lambda$, which is not the case here (particle diameter is about 1/4 of the wavelength ). Compton scattering is irrelevant due to the low energy of the photons.

EDIT: Could perhaps Raman scattering be playing a role?


Perhaps you may want to consider Mie scattering. It includes the possibility for scattering when the sizes of the partilces are close to the wavelength of the light. It also includes Rayleigh scattering in the limit of small particles.

  • $\begingroup$ Shouldn't this be a comment, and not an answer? $\endgroup$ – Marcel Jan 3 '17 at 19:49

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