I Electric dipole moment of the nucleus of an atom

[tamir]

TL;DR Summary

Why is the electric dipole moment of the nucleus of an atom equal zero?

Summary: Why is the electric dipole moment of the nucleus of an atom equal zero?

Summary: Why is the electric dipole moment of the nucleus of an atom equal zero?

I read about the hyperfine interactions that cause the altering of the energy levels of the nuclues of an atom. Under the discussion about monopole and quadrupole interactions, the term of the dipole moment interaction was determined to be zero because the nucleus has no electric dipole moment. My question is, what are the assumptions leading to this result? It seems like the only assumption that was taken into account was the nucleus being a positive charge distibution and it does not make sense to me considering the expression of the electric dipole moment. I would assume that some sort of symmetry of the nucleus need to be considered as well.

 

[Vanadium 50]

Are you asking about Schiff moments or T-violation?

 

[tamir]

Are you asking about Schiff moments or T-violation?

To my understanding it is more simple than that.
The nucleus is considered as merely a charge distribution and the electrostatic energy of the interaction between the nucleus and the electron is approximated using multipole expansion.
What I do not understand is, what are the assumptions that result with the dipole term being zero?

 

[Vanadium 50]

Well, one would be T-symmetry. The other would be the Schiff moment.

 

[tamir]

Well, one would be T-symmetry. The other would be the Schiff moment.

Can you refer me to literature of those subjects?
I must admit that it seems a little bit over the top, because what I read involved more basic concepts.
As I wrote at my post, I would have assumed that some sort of symmetry of the charge distribution of the nucleus leads to its electric dipole moment being zero.

 

[Vanadium 50]

Can you refer me to literature of those subjects?

Can you tell me where you have already looked?

I would have assumed that some sort of symmetry of the charge distribution of the nucleus leads to its electric dipole moment being zero.

And had you Googled "Schiff moment" (which I note in passing is the third time I wrote this) you would have learned about this. I can point you in the right direction, but I can't pour knowledge into your head.

A guy prays: "Dear Lord, please make me win the lottery."
The following day he begs the Lord again: "Please make it so I win the lottery, Lord!"
The next day, he again prays: "Please, please, dear Lord, make me win the lottery - you know how much I need the money."
Suddenly there is a thunderclap and a booming voice from the heavens: "Work with me here. Buy a doggone ticket!"