Elastic scattering by a metal sphere with an adsorbed molecule as a model for the detection of single molecules by scanning probe enhanced elastic resonant scattering (SPEERS)

It was shown previously that by scanning near-field optical microscopy (SNO M) using the tetrahedral tip (T-tip) as a probe it was possible to obtain i mages of metal nanoparticles at a resolution below 10 nm. Therefore we star ted to investigate whether it is possible to obtain images of single dye mo lecules at a resolution below 10 nm. A model is proposed for the detection of single molecules by SNOM by a probe enhanced elastic resonant scattering process. Local plasmon excitation of the T-tip is suggested to lead to a l arge enhancement of the elastic resonant scattering signal of a dye molecul e.