The highly excited C - H stretching states of CHD 3 , CHT 3 , and CH 3 D

Unlike many other molecules having local modes, the highly excited C-H stretching states of CHD3 show well resolved experimental spectra and simple Fermi resonance behavior. In this paper the local mode features in this prototype molecule are examined using a curvilinear coordinate approach. Theory and experiment are used to identify the vibrational state coupling. Both kinetic and potential terms are employed in order to characterize the coupling of the C-H stretch to various other vibrational modes, notably those including D-C-H bending. Predictions are also made for CHT 3 and the role of dynamical coupling on the vibrational states of CH3D explored. Implications of these findings for mode-specific and other couplings are discussed.