Determination of atomic scattering lengths from measurements of molecular binding energies near Feshbach resonances

Understand

We present an analytic model to calculate the atomic scattering length near a Feshbach resonance from data on the molecular binding energy.

• Our approach considers finite-range square-well potentials and can be applied near broad, narrow, or even overlapping Feshbach resonances.
• We test our model on Cs$_2$ Feshbach molecules.
• We measure the binding energy using magnetic-field modulation spectroscopy in a range where one broad and two narrow Feshbach resonances overlap.