Fermi resonance between the vibrations of the hydrogen atom adsorbed at the (111) face of the diamond surface

The phenomenon of the Fermi resonance between the stretching and bending vi brations of the hydrogen atom adsorbed at the (111) face of the diamond sur face is studied quantum-mechanically. The wave functions for the motion of the hydrogen atom were obtained by means of diagonalization of the 3D Hamil tonian with the potential energy surface calculated by the method of quantu m chemistry at the nonempiric level for the HC(CH3)(3) cluster. The analysi s of vibrational states of the hydrogen atom shows that the stretching vibr ation of the C-H bond interacts strongly with the second overtone of the de formation C-C-H vibration (the Fermi resonance). The matrix element of the coordinate between the vibrational levels is shown to be strongly dependent on the anharmonicity of the potential of the C-H bond. The influence of th e Fermi resonance on the mechanism of the energy relaxation of the C-H vibr ation is discussed.