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On this website http://bingweb.binghamton.edu/~suzuki/QuantumMechanicsFiles/2-4_Polarization_of_photon_emitted_from_an_excited_atom.pdf#page72 they want to explain the selection rules and the polarisation of the photon in a more classical way. But if look at the following dipole transition enter image description here

we can see that $\Delta m=1$ and therefore the photon should be circularly right polarized. But does this not harm the conservation of angular momentum and are the photons not emitted in all spatial directions?

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  • $\begingroup$ The spin of the electron has to do with the deflection in magnetic fields and with the orientation between electrons. The spin of the photon has to do with the direction between the photons electric to its magnetic field component. In this sense these spins are totally different things. Only a rotating electron passes on a part of its torque to the emitted photon. The two E and M field components of the photon are then (in vacuum) still oriented 90° to each other, but rotate together in the axis of motion of the photon. $\endgroup$ Feb 10, 2022 at 4:44
  • $\begingroup$ @HolgerFiedler So does this mean that it‘s not possible to understand the connection between $\Delta m$ and the polarisation of the photon in a classical way? $\endgroup$
    – Silas
    Feb 10, 2022 at 10:23

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The spin of the electron has to do with the deflection in magnetic fields and with the orientation between electrons. The spin of the photon has to do with the direction between the photons electric to its magnetic field component. In this sense these spins are totally different things.
Only a rotating electron passes on a part of its torque to the emitted photon. The two E and M field components of the photon are then (in vacuum) still oriented 90° to each other, but rotate together in the axis of motion of the photon.

Polarization of photons occurs when charges are accelerated in the same direction. If the photons are accelerated upwards, then the electric field component of the emitted photons also points upwards and the magnetic field component is perpendicular to E (and to the propagation direction of the photons). This is the process as it is actually detectable for antenna radiation.

What I don't know - but is worth a question on PSE - is whether the spin of the electrons aligns during accelerations (in the antenna rod). If so, then it is prediction that the spin tilts towards the perpendicular with respect to the acceleration direction.

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