Detection of surface structural changes during adsorption events using two-trace two-dimensional (2T2D) correlation spectroscopy

摘要

We demonstrate a method by which a pair of spectra acquired using surface-sensitive second-order nonlinear vibrational spectroscopy, visible-infrared sum-frequency generation, can be analyzed in order to readily determine whether changes that occur as a result of varying environmental conditions results in a change in the population of surface molecules, or a structural rearrangement of the surface. This is accomplished via two-trace two-dimensional correlation analysis, a recently developed technique that uses spectral phase information to provide a level of comparison beyond what can be achieved by simple spectral subtraction or division. While surface reorientation and/or a change in the degree of ordering are often dif fi cult to detect from spectra obtained in a single beam polarization, without detailed analysis of the lineshape, we show that such changes provide strong asynchronous cross peaks in the frequency correlation map. (c) 2020 Elsevier B.V. All rights reserved.