  Considerable insights can be obtained regarding the nature of highly excited
states by computing the eigenbasis expectation values of the resonance
operators associated with an effective spectroscopic Hamiltonian. The
expectation values are related to the parametric derivative of the eigenvalues
with respect to specific resonance strengths i.e., level velocities.Sensitivity
of the level velocities to the existence of closed orbits in the underlying
classical phase space provides for a dimensionality independent route to a
dynamical assignment of the states. In this letter, taking CHBrClF (polyad P=5)
and the [16,0]^{g+} bend polyad of C_{2}H_{2} as examples, we show that the
level velocities can signal the birth of new modes and highlight sequences of
localized eigenstates.
