A temporal study of the surface enhanced Raman bond polarizabilities of ethylene thiourea on the Ag electrode: The electromagnetic and charge transfer mechanisms

Based on the surface enhanced Raman intensities of ethylene thiourea on the silver electrode, the temporal bond polarizabilities are elucidated to offer important information of the surface enhancement mechanisms. The results demonstrated that both the electromagnetic and charge transfer mechanisms are responsible for the large enhancement. The relaxation rates of the various bond polarizabilities are displayed. All obey a single exponentially decaying function, independent of potentials and mechanisms. The characteristic time for the relaxation due to charge transfer mechanism is larger than that via the electromagnetic mechanism due to that its relaxation requires longer time for the charges to re-distribute.