Adiabatic magnetoassociation of KRb Feshbach molecules*

We study the creation of Fermionic $^{40}$K$^{87}$Rb Feshbach molecules via magnetoassociation. Two types of behavior can be accessed by varying the magnetic field sweep rate. In the nonadiabatic limit where few molecules are created, pair formation is governed by Landau-Zener physics. This intuitive two-body picture breaks down at the other extreme, where adiabatic molecule creation efficiency saturates below unity. A better understanding of this efficiency is useful for experiments where Feshbach molecules are a first step, such as the creation of ground state polar molecules.