Optical imaging and tracking of single molecules in ultrahigh vacuum

TL;DR

This paper demonstrates a fluorescence imaging technique adapted for ultrahigh vacuum conditions, enabling the observation of single molecule dynamics on surfaces with high resolution, advancing surface science studies.

Contribution

It introduces a novel method combining fluorescence imaging with ultrahigh vacuum, allowing detailed tracking of single molecules on surfaces, which was not previously possible.

Findings

Resolved surface adsorption and diffusion of single molecules

Identified two characteristic decay time scales in fluorescence signals

Proposed a simplified model explaining molecule-surface interactions

Abstract

Molecule-surface interaction is key to many physical and chemical processes at interfaces. Here, we show that the dynamics of single molecules on a surface under ultrahigh vacuum can be resolved using fluorescence imaging. By adapting oil-immersion microscopy to a thin vacuum window, we measure the surface adsorption, translational and rotational diffusion of single perylene molecules on a fused silica surface with high spatial and temporal resolutions. Time-dependent measurements of the fluorescence signal allow us to deduce two characteristic decay time scales, which can be explained through a simplified model involving two adsorption states and five energy levels. The system presented in this work combines fluorescence imaging with essential ingredients for surface science and promises a platform for probing single molecule-surface interactions in highly defined conditions.