To arrive at a quantitative description of the JT effect, the forces appearing between the component wave functions are described by expanding the Hamiltonian in a power series in the Q i . Owing to the very nature of the degeneracy, the Hamiltonian takes the form of a matrix referring to the degenerate wave function components. A matrix element between states Ψ Ψ a and Ψ Ψ b generally reads as: