Evolution of Attractive Bose Polarons Near a Feshbach Resonance

We investigate how Bose polarons asymptotically evolve into Feshbach molecules as a function of interaction strength. We create Bose polarons by immersing fermionic impurities in a Bose-Einstein condensate. Using spatially resolved RF spectroscopy, we probe the energy and spectral width of the transition from an initial attractive polaron on the attractive side of the resonance, to three different final states, repulsive polaron, Feshbach molecule, and attractive polaron on the repulsive side of the resonance. We observe the attractive polaron to smoothly crossover into a Feshbach molecule. Multi-phonon resonances predicted in some theoretical predictions are not observed. The smooth connection between polarons and Feshbach molecules also opens up pathways for direct photoassociation of free polarons into more tightly bound molecules.