An HREELS study of pi* and sigma* negative ion resonances of c(8x2) benzoate on Cu(110)

摘要

For the c(8x2) benzoate on Cu(110) system, multiple unoccupied states have been measured through negative ion resonances by high-resolution electron-energy-loss spectroscopy (HREELS). Based on the azimuthal and polar angle dependences, we assign contributions from B-2 and A(1) states to a resonant feature in the [001] direction and contributions from B-1 and A(1) states in the [110] direction. The B-2 state is observed close to 4.7 eV and the B-1 feature is centered at 6.5 eV. The angular and azimuthal dependence of the C-H stretch intensity in HREELS at resonance is consistent with their assignment and the results of ab initio calculations. Overtone intensity shows an exponential decay as a function of overtone quantum number. From the overtone frequencies, an anharmonicity of 0.0272 is obtained which leads to a dissociation energy of the C-H bond of about 81 kcal/mol. (C) 1998 American Institute of Physics. [References: 42]