# Homework Help: Energy difference between energy levels with same n

1. Jan 18, 2010

### Kris2456

1. The problem statement, all variables and given/known data

I am somewhat confused about calculating the energy difference between different energy levels with the same principal quantum number (n). Eg. one of the questions that I have requires me to work out the energy difference between 23P2 state and the 23S1 state.

2. Relevant equations

I think this equation from Wikipedia may be relevant:

3. The attempt at a solution

If i interpret Hund's rules correctly, the 23P2 state is lower in energy since it has a higher value of L.
My attempt at getting the value of the energy difference between the levels involved using the "fine structure" part of the above equation to work out the difference using 1 & 2 for the values of J.

The value I get is 2.42e-15 eV which corresponds to a frequency of 5.84 Ghz (the question is about metastable helium being cooled by a laser). I have tried to find correct values for this on the internet but have had little luck :(

Last edited: Jan 18, 2010