  A novel atom-molecule conversion technique has been investigated. Ultracold
85Rb atoms sitting in a DC magnetic field near the 155G Feshbach resonance are
associated by applying a small sinusoidal oscillation to the magnetic field.
There is resonant atom to molecule conversion when the modulation frequency
closely matches the molecular binding energy. We observe that the atom to
molecule conversion efficiency depends strongly on the frequency, amplitude,
and duration of the applied modulation and on the initial phase space density
of the sample. This technique offers high conversion efficiencies without the
necessity of crossing or closely approaching the Feshbach resonance and allows
precise spectroscopic measurements.
