Fig. 2: Near-field experiment to measure field-enhanced molecular scattering.

\({{{\bf{E}}}}^{{{\rm{in}}}}\): Incident field polarized along the antenna long axis, \({p}_{{{\rm{A}}}}\): Induced dipole moment in the antenna. \({{{\bf{E}}}}^{{{\rm{sca}}}}\): Scattered field, PDMS: Polydimethylsiloxane. Dashed lines illustrate the near-field coupling between antenna and tip, which is modulated by varying sinusoidally the tip-antenna distance, \(d(\varOmega )\), at frequency \(\varOmega\).