Single-Molecule Microscopy in Ultrahigh Vacuum

Optical microscopy of single molecules is widely applied in studying dynamic processes with simultaneously high spatial and temporal resolutions under ambient conditions, such as cell membranes [1] and catalyst structures [2]. A prerequisite for achieving these high resolutions is to efficiently collect photons emitted from the object [3], which is commonly solved by applying high numerical aperture (NA) objectives and immersion oil. However, it is rather challenging to implement similar constructions for ultrahigh vacuum (UHV) applications, because of the outgassing of the imaging optics and the oil. In this work, we demonstrate that efficient photon collection can be achieved for single molecules on a surface in ultrahigh vacuum. This opens the possibility to combine optical microscopy with conventional surface science experiments.