Resonance fluorescence is an important means to investigate radiation-atom interaction.
Of special interest is the spectrum of resonance fluorescence of a single trapped ion excited by low intensity, monochromatic laser light. This narrow bandwidth has allowed us to spectroscopically isolate the elastically scattered component of fluorescence, which is coherent with the laser field. Under the same experimental conditions we observed also antibunched photon statistics. The combination of both detection schemes provides the possibility of observing squeezing, one of the most fundamental nonclassical effects predicted by the theory of resonance fluorescence. The wave detection demonstrates the properties of a classical atom, i.e. a driven oscillator, whereas the particle or photon detection shows the quantum properties of the atom.