# Polarization of an emitted photon

• naima
In summary, questions were raised about the polarization of an emitted photon from an excited electron returning to its ground state, specifically if it has circular polarization around z. It was discussed that the total angular momentum of the electron must be taken into consideration, and that the photon would have right-handed circular polarization if it is traveling along z. Additional information on photon angular momentum and vector spherical harmonics was recommended for further understanding.

#### naima

Gold Member
Bonnes fetes de Noel.

When an excited electron returns to its ground state a photon is emitted.
Suppose that the electron's spin skip from +1/2 to -1/2 (around z)and that the photon has a momentum parallel to z.
I suppose that this photon has a circular polarization around z (Is it true?)
The problem is that there is no spin alone conservation but total angular momentum conservation.
Knowing all about |e> and |g> what can we calculate about the polarization of the emitted photon?

Last edited:
naima said:
Bonnes fetes de Noel.
Merci !

naima said:
When an excited electron returns to its ground state a photon is emitted.
Suppose that the electron's spin skip from +1/2 to -1/2 (around z)and that the photon has a momentum parallel to z.
I suppose that this photon has a circular polarization around z (Is it true?)
To first order, the spin of the electron is not coupled to the electromagnetic field, so spin-flip doesn't occur during transtions. Look up selection rules.

naima said:
The problem is that there is no spin alone conservation but total angular momentum conservation.
Knowing all about |e> and |g> what can we calculate about the polarization of the emitted photon?