Quantitative Sampling of Atom-Scale Terahertz Waveforms

Atomic light-matter interaction depends critically on the absolute strength and the precise time evolution of the near field, which may be strongly influenced by quantum-mechanical effects. Yet, quantitatively measuring ultrafast near-field waveforms on atomic scales has remained an open challenge. Using a molecular switch as a local field sensor, we sample the temporal shape and strength of atomically confined light field transients.