Level repulsion in a two-level Hamiltonian
= Level repulsion in a two-level Hamiltonian
The eigenvalues of $\left(\begin{smallmatrix}E_1&h\\h&E_2\end{smallmatrix}\right)$ are their mean plus or minus $\sqrt{(E_2-E_1)^2/4+h^2}$, so nonzero coupling increases their separation.