The expectation values of resonance operators can help to elucidate the mechanisms that underlie complicated, multidimensional vibrational dynamics, as represented by effective Hamiltonian models.
Jacobson, M. P., & Field, R. W. (2000). Visualizing intramolecular vibrational redistribution: Expectation values of resonance operators. Chemical Physics Letters, 320(5–6), 553–560. https://doi.org/10.1016/S0009-2614(00)00306-7