Shifts Of Vibrational Modes Research Articles

Vibrational-mode shifts in inelastic electron tunneling spectroscopy: Effects due to superconductivity and surface interactions

Measurements of the effect of the top metal electrode on the vibrational-mode energies of benzoic acid on aluminum oxide with Pb, Sn, and Ag top metal electrodes are described. Peak shifts of approximately 15 meV for the O-H stretch modes of hydroxyl ions, 0.5 meV for the C-H bending modes, and less than 0.2 meV for the C-C ring stretch and bend modes of benzoate molecules were found. These measurements are discussed in terms of a simple image model. For junctions with superconducting electrodes a modulation-dependent correction must be made to the measured peak positions. A theory is developed for the line shapes and peak positions of both the second and third harmonic signals and compared with experiment.

Raman scattering from GaS xSe 1- x

The non resonant Raman scattering spectra of GaSe, GaS and of eight different mixed crystals GaS x Se 1- x are presented. The frequencies of some vibrational modes shift continuosly from GaSe to GaS indicating that the mixed crystals are homogeneous. The discontinuous shift of some other modes is explained either by the change of the stacking of the layers, or by a ‘two mode’ behaviour as previously observed in other types of mixed crystals. Moreover, local vibrational modes are observed.