  The scattering length is commonly used to characterize the strength of
ultracold atomic interactions, since it is the leading parameter in the
low-energy expansion of the scattering phase shift. Its value can be modified
via a magnetic field, by using a Feshbach resonance. However, the effective
range term, which is the second parameter in the phase shift expansion,
determines the width of the resonance and gives rise to important properties of
ultracold gases. Independent control over this parameter is not possible by
using a magnetic field only. We demonstrate that a combination of magnetic and
electric fields can be used to get independent control over both parameters,
which leads to full control over elastic ultracold interactions.
