Spin-flip of lithium core electrons

[Northprairieman]

Hydrogen electrons can spin-flip and emit a 21 cm photon. Can core electrons in a metal like lithium spin flip? If so, is the energy required to do so similar to hydrogen?

 

[Vanadium 50]

There are two core electrons in lithium, and they have to be spinning in opposite directions. If you flip one, you have to flip the other, so the net result is no change.