A quantum mechanical approach to an analytical expression of the single-molecule-single-nanoparticle surface enhanced raman scattering

A quantum mechanical theory elucidating the single-molecule-single-nanoparticle surface enhanced Raman scattering (SERS) process is proposed. The theory attributes the principal mechanism of the process to an increase of the spontaneous emission rate of a molecule adsorbed to a nanoparticle due to the enhanced local electromagnetic field and the Purcell effect. The result is a first-ever analytical expression for the single-molecule-single-nanoparticle SERS enhancement factor in good agreement with experiment.