Ultrafast, Multidimensional attenuated total reflectance spectroscopy of adsorbates at metal surfaces

Abstract

Ultrafast dynamics of molecules at solid-liquid interfaces are of outstanding importance in chemistry and physics due to their involvement in processes of heterogeneous catalysis. We present a new spectroscopic approach to resolve coherent, time-resolved, two-dimensional (2D) vibrational spectra as well as ultrafast vibrational relaxation dynamics of molecules adsorbed on metallic thin films in contact with liquids. The setup is based on the technique of Attenuated Total Reflectance (ATR) spectroscopy which is used at interfaces between materials that exhibit different refractive indices. As a sample molecule we consider carbon monoxide adsorbed in different binding configurations on different metals and resolve its femtosecond vibrational dynamics. It is presented that mid-infrared, multi-dimensional ATR spectroscopy allows for obtaining a surface-sensitive characterization of adsorbates’ vibrational relaxation, spectral diffusion dynamics and simple inhomogeneity on the femtosecond timescale.