The relaxations of temporal bond polarizabilities of methylviologen adsorbed on the Ag electrode by 514.5 nm excitation: a Raman intensity study

摘要

An algorithm to elucidate the temporal bond polarizabilities from the surface enhanced Raman (SERS) intensities was employed to the case of methylviologen (MV) adsorbed on the Ag electrode. This enables us to obtain the properties of its SERS mechanisms and the effect of its adsorption. The analysis shows that the charge transfer and electromagnetic mechanisms involving in this MV SERS system possess different relaxation times for its various temporal bond polarizabilities. The physics is that the process involved in the charge transfer mechanism will take longer time than that involved in the electromagnetic mechanism since it needs more time to redistribute the charges during relaxation. The time division between these two mechanisms is figured out to be around 3 ps for this system. Adsorption also enhances the relaxation of the temporal bond polarizabilities, in general. The adsorption effect is indicated by the temporal bond polarizabilities close to the final stage of relaxation. They are, in fact, the quantities parallel to the bond electronic densities in the molecular orbital (MO) concept. For comparison, the case of IVIV solid was also analyzed.