Three-body radio-frequency association of Efimov trimers

We present a theoretical analysis of rf association of Efimov trimers in a two-component Bose gas with short-range interactions. Using the adiabatic hyperspherical formalism to solve the quantum three-body problem, we obtain universal expressions for three-body rf association rates as a function of the s-wave scattering length a > 0. We find that the association rates scale as a(-2) in the limit of large a, and diverge as a(3)a(ad)(3) whenever an Efimov state crosses the atom-dimer threshold (where a(ad) stands for the atom-dimer scattering length). Our calculations show that trimer formation rates as large as similar to 10(-21) cm(6)/s can be achieved with rf Rabi frequencies on the order of 1 MHz, suggesting that direct rf association is a powerful tool for making and probing few-body quantum states in ultracold atomic gases.