Hello! I am answering a problem which involves spins in the hamiltonian. The hamiltonian is given by H = B(a1Sz^(1) + a2Sz^(2)) + λS^(1)dotS^(2). The Sz^(1) and Sz^(2) refers to the Sz of the 1st and 2nd spins respectively. B is the magnetic field and the others are just constants. The question is to use the 2nd order perturbation theory to approximate the energy eigenvalues, given that the second term is the perturbing potential. Also it says that the problem is solvable exactly, so that the answer can be verified. I haven't been exposed to spins and its hamiltonian or eigenvalues. Please suggest a detailed way of attacking this proble. Thanks a lot!