The highly excited C–H stretching states of CHD3, CHT3, and CH3D

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 CHT3 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.