2DIR Spectroscopy for Studies of Molecular Structure and Dynamics on Surfaces of Noble Metals

Abstract

Ultrafast studies of molecular dynamics using femtosecond two-dimensional vibrational spectroscopy (2DIR) provide unique insights on molecular interactions. Recently, such studies were extended from bulk samples to molecules on surfaces of noble metals, including disordered and engineered nanostructures. The metal nanostructures provide field enhancement allowing sensitive measurements at interfaces, but they also alter the molecular dynamics. 2DIR measurements at interfaces reveal correlations between vibrational transitions and rates of the vibrational relaxation, dephasing, spectral diffusion, and resonant energy transfer. At the surfaces, molecular dynamics and interaction with the environment can be modified by geometrical constrains associated with tethering, by the interaction between the molecule and the substrate, or by the enhanced near-fields associated with the metal. Interestingly, in many cases, these anticipated effects were found to be absent or fade away already at the microscopic distances away from the surface. Herein, we provide an overview of recent experimental studies in the field.