Abstract

We present a microscopic theory to study Raman scattering of a molecule embedded within the palsmonic nanogap cavity in a tip-enhanced Raman spectroscopy instrument. We find that the strong near-field self-interaction of molecule with the plasmonic nano-gap strongly modulates the Raman excitation and radiation in both the signal intensity and spatial sensitivity, with a modification factor of g(r). The Raman enhancement factor is now given by G = g⁴ | E / E₀ |⁴. As a result, a plasmon-molecule “super-hot spot” is created within the nanogap, leading to the sub-nanometer lateral resolution of Raman mapping.

© 2015 Optical Society of America