PUMP-PROBE EXPERIMENTS WITH A SINGLE-MOLECULE - AC-STARK EFFECT AND NONLINEAR-OPTICAL RESPONSE

We have measured the ac-Stark effect on single terrylene molecules in p-terphenyl crystals at superfluid helium temperatures. With the pump beam far enough from resonance, the molecular transition shifts as exp ected, i.e., proportional to the pump intensity and to the inverse pum p detuning. Experiments closer to resonance with stronger beams show A utler-Townes-like structures that can be well reproduced by means of B loch equations with two intense laser fields. These experiments are a demonstration of nonlinear optical effects with the localized electron ic states of a single molecule trapped in a solid.