The low-lying levels of 13-N are the ground state, 1/2-; 2.37 MeV, 1/2+; 3.51 MeV, 3/2-; and 3.55 MeV, 5/2+. The next states are about 6.5 MeV and above. Interpret these four states according to the shell model.
How should I even begin this problem? Is there any general formulas which I should apply?