First off, I'm glad I'm finally a member on this board. It has helped me TREMENDOUSLY over the past few years with various problems I've had. You guys/gals are awesome and hopefully I can make some contributions to this site. 1. The problem statement, all variables and given/known data A. Write down the partition function for positronium, assuming that only the levels illustrated in the diagram exist. Evaluate the partition function for T=20000K. Remember to include the degeneracies for each level. (I couldn't figure out how to copy and paste the diagram I was given, so I googled the one below. It's the same diagram, but the diagram I was given stops at the N=3 energy level) B. Write down an expression for the probability that the atom will exist in the state given by N=3, l=1, and determine that probability for T=20000K C. Find an expression for the mean energy and evaluate that expression for T=20000K 2. Relevant equations 1. En = 6.803eV (1 - 1/n2) 2. Z= ∑e-E(s)/KT 3. P(s)= 1/z * e-En/KT 4. ∑ E(s)* P(s) 3. The attempt at a solution A. So, we haven't done anything even close to this in class, so I'm a little coonfused, but to start, I substituted eq1 into the partition function in eq2 to get Z= ∑e-6.803eV (1 - 1/n2)/KT. After this, I'm completely stuck because we didn't really cover degeneracy in class very well. I know I'm supposed to multiply the expression by the degeneracy, but I'm not exactly sure how to do that. B. Once A is found, this should be straightforward C. Once A is found, this should be straightforward My work is due by 11/25 at 5pm (EST), any help would be greatly appreciated!