Effective Atom–Molecule Conversions Using Radio Frequency Fields

The present study is inspired by the Wieman group experiment [Phys. Rev. Lett. 2005, 95, 190404], in which they use a slow modulated magnetic field to effectively transfer rubidium atoms into cold molecules near a Feshbach resonance. We develop a time-dependent collision theory based on two channel model potentials to study the atom–molecule population transfer induced by a single-color radio frequency field in an ultracold ⁸⁷Rb gas. Wave-packet dynamical simulations allow an investigation of both bound–bound transitions and free–bound transitions. The effects of temperature, detuning and the RF amplitude on the population transfer are discussed in detail. Some of our simulations suggest that oscillatory atom–molecule conversion could originate from the long coherence time of the wave packet. This coherence time is unusually long in ultracold gases because the collision energy is typically quite well-defined.