# A question on momenta of electrons

1. Dec 13, 2005

### rushil

Is there any special significance of the fact that $$\vec{L}$$ and $$\vec{S}$$ of an electron are in-phase or out-of-phase at all times?????

i.e. is there any special physical significance of the fact that

(i) $$| \vec{J} | = | \vec{L} | + | \vec{S} |$$
(ii) $$| \vec{J} | = | \vec{L} | - | \vec{S} |$$
I am refering to magnitudes above!
Also, is there any significance of the fact that $$\vec{L}$$ and $$\vec{S}$$ are NOT in phase at any time?????
We are obviously assuming simple electronic configurations! :tongue:

2. Dec 13, 2005

### Physics Monkey

The total angular momentum is always $$\vec{J} = \vec{L} + \vec{S}$$, the rule you refer to has to do with the allowed values of the $$J^2$$ quantum number.

3. Dec 13, 2005

### rushil

Can you please explain a bit more!!!

4. Dec 13, 2005