Gamma Decay (Electric and Magnetic Transitions)

[says]

I'm trying to understand electric and magnetic transitions in gamma decay a bit more intuitively than i currently understand but I'm having a really hard time doing so

When the nucleus is coupling to the electric field of the
photon we call it an electric decay and the parity is: (-1)^L

When the nucleus is coupling to the magnetic field of the
photon we call it a magnetic decay and the parity is -(-1)^L

What does it mean by saying the nucleus 'couples' to the electric field or magnetic field?

 

[LightHero]

How does this result in a parity change?When we talk about the nucleus coupling to the electric or magnetic field of the photon, we mean that it is interacting with the electric or magnetic field in a way that causes the nucleus to undergo a transition from one state to another. The parity change is a result of this interaction. It happens because the electric and magnetic fields of the photon have different effects on the nucleus depending on its spin and angular momentum. In an electric transition, the electric field of the photon interacts with the electric dipole moment of the nucleus, causing the nucleus to flip its spin and angular momentum and thus resulting in a parity change. In a magnetic transition, the magnetic field of the photon interacts with the magnetic dipole moment of the nucleus, which can also cause the nucleus to flip its spin and angular momentum and thus resulting in a parity change.