Possible rationale for ultimate enhancement factor in single molecule Raman spectroscopy

The Purcell’s original idea [E.M. Purcell, Phys. Rev. 69 (1946) 682] on modification of photon spontaneous emission rate is extended to modification of photon spontaneous scattering rate. Simultaneous account for local incident field and local density of photon states enhancements in close proximity to a silver spheroid is found to provide up to 1014-fold Raman scattering cross-section rise up. A model of the so-called ‘hot spots’ in surface enhanced spectroscopy is elaborated as local areas with high Q-factor at incident and scattered (emitted) light frequencies. Transient Raman experiments are proposed towards verification of the model.