  Experimental control of magnetic Fano-Feshbach resonances in ultracold
$^{40}$K Fermi gases, using radio-frequency (RF) fields, is demonstrated.
Spectroscopic measurements are made of three molecular levels within 50 MHz of
the atomic continuum, along with their variation with magnetic field. Modifying
the scattering properties by an RF field is shown by measuring the loss profile
versus magnetic field. This work provides the high accuracy locations of ground
molecular states near the s-wave Fano-Feshbach resonance, which can be used to
study the crossover regime from a Bose-Einstein condensate to a
Bardeen-Cooper-Schrieffer superfluid in presence of an RF field.
