I Rayleigh scattering and reversibility

[J O Linton]

TL;DR

Is Rayleigh scattering a reversible process?

In many books and websites the elastic (Rayleigh) scattering of low energy photons off an atom is stated as being reversible. It seems to me that it is a mistake to think that all elastic processes are reversible. If a process is reversible it should be possible to calculate the initial state of the system given the final state. This is not the case with RS because the emitted photon can be emitted in any direction at random so there is no way of calculating the direction it was originally moving in.
If RS is an irreversible process then it would provide the ideal candidate for the random element which is required to explain the success of Boltzmann's statistical theory of gases and the Second Law of Thermodynamics. Is there something wrong with this argument?

 

[tech99]

I should have thought that a single scattering particle acts as a dipole re-radiator, so if we know its geometry and orientation, then the characteristics of the scattered wave can be calculated. I am not sure that Rayleigh scattering is necessarily a quantum process as it can occur with long wavelengths and correspondingly large objects - the attenuation between source and detector will be the same in both directions (Rayleigh-Carson law of reciprocity) and so is reversible. Of course, no optical system of source-detector if operated with single photons can be predicted from moment-to-moment and so is non reversible.