The charge transfer mechanism in the SERS of 2-methylpyrazine on silver electrode

SERS spectra of 2-methylpyrazine have been recorded on silver electrode in a range of potential from 0.00 to -0.75 V vs. a saturated Ag/AgCl/KCl refer ence electrode. The so obtained spectra have been compared with the Raman o f the aqueous solution and the observed differences between the relative in tensities of Raman and SERS spectra have been interpreted on the bash; of a charge transfer mechanism. The most enhanced bands correspond to modes tha t relate the equilibrium geometries of the neutral molecules and its anion radical, while the behaviour of other less enhanced bands is due to vibroni c coupling between the ground state of the anion radical and other of its p ossible excited states, in order to check this enhancement mechanism, we ha ve used the theoretical results provided by ab initio calculations on the n eutral molecule and its anion radical. (C) 1999 Elsevier Science B.V. All r ights reserved.