Formation of fermionic molecules via interisotope Feshbach resonances

We perform an analysis of recent experimental measurements and improve the lithium interaction potentials. For 6Li a consistent description can be given. We discuss theoretical uncertainties for the position of the wide 6Li Feshbach resonance, and we present an analytic scattering model for this resonance, based on the inclusion of a field-dependent virtual open-channel state. We predict new Feshbach resonances for the 6Li-7Li system, and their importance for different types of crossover superfluidity models is discussed