Transient two-ion chaos

Transient order→chaos transitions of two ${\mathrm{Ba}}^{+}$ ions are observed where the duration of the chaotic state increases smoothly with an increasing Mathieu control parameter q. The transient regime precedes the transition point ${\mathit{q}}_{\mathit{c}}$ for stationary chaos, which is well defined and reproducible. The perturbative step that initiates chaos takes place on a time scale of 1 min, far longer than previous estimates, and is due to a single ${\mathrm{H}}_2$-${\mathrm{Ba}}^{+}$ collision (${\mathrm{H}}_2$ pressure 5×${10}^{\mathrm{-}11}$ Torr). In contrast to random collision events, chaos can be initiated deterministically by a new pulse technique. These observations resolve earlier anomalies and challenge computer simulations.