Can a Single-Pulse Standing Wave Induce Chaos in Atomic Motion?

We measure momentum transferred from a single pulse of a standing wave of light to a sample of ultracold sodium atoms, and observe a sharp increase in the momentum transfer when the pulse duration exceeds a critical value ${\tau }_{\mathrm{cr}}$. A classical analysis of nonlinear resonances shows that resonance overlap occurs at ${\tau }_{\mathrm{cr}}$, and there is a transition to global classical chaos. These results are a direct experimental test of the “resonance overlap criteria” and illustrate that even the turning on and off of a simple spatially periodic interaction can lead to surprising and novel results.