Rayleigh one-two photon, dipole approx

[evidenso]

Hello
Im having 2 questions
I'm investigating NIR light propagation in tissue such as the skin and my question is:

In dipole aprox: Absorption, emission and normal Raman scattering is one-photon processes. But what is Rayleigh scattering?

When light hit a small molecule the dipole approximation is good. But what if the single molecule
is large like a protein. What happens then to the absorption/emission/raman transitionprobability (fermis golden rule, Kramer-Heisenberg disp relation)?

 

[evidenso]

no one ? ;)

 

[denian]

Hello,

Thank you for your questions. I am happy to provide some information about Rayleigh scattering and its relationship to the dipole approximation.

Rayleigh scattering is a phenomenon in which light is scattered by particles or molecules that are much smaller than the wavelength of the incident light. This scattering occurs in all directions and is responsible for the blue color of the sky. In the dipole approximation, the scattering is considered to be elastic and the scattered photons have the same energy as the incident photons.

In terms of absorption, emission, and Raman scattering, these processes are considered to be one-photon processes in the dipole approximation. This means that a single photon is involved in the transition between energy levels in the molecule. However, in Rayleigh scattering, no energy level transitions occur and the scattered photons have the same energy as the incident photons. Therefore, Rayleigh scattering is not considered to be a one-photon process in the dipole approximation.

When considering larger molecules, such as proteins, the dipole approximation may not be as accurate because the molecule's size and shape can affect its electronic structure and the distribution of charge. In this case, the absorption, emission, and Raman scattering processes may involve multiple photons and cannot be accurately described by Fermi's golden rule or the Kramer-Heisenberg dispersion relation. More complex theoretical models, such as the coupled dipole approximation, may be needed to accurately describe these processes in larger molecules.

I hope this helps answer your questions. If you have any further inquiries, please feel free to ask. Thank you for your interest in this topic.