Emission frequency of single molecules at a metallic aperture: the applicability of the image theory

Abstract

The simple classical image theory is applied to describe the shift in emission frequencies for single molecules at a metallic aperture. The validity of this approach is further clarified using well known results for the case of molecules at flat surfaces. For molecules oriented parallel to the plane of the aperture, a numerical example shows that aside from the general small red shift, the two orthogonal “in-plane” directions behave quite differently in their emission frequencies as they are scanned from the center to the edge of the tip, suggesting a possible way of distinguishing the two orientations through observation of their emission frequencies.