  The conversion of ultracold atoms to molecules via a magnetic Feshbach
resonance with a sinusoidal modulation of the field is studied. Different
practical realizations of this method in Bose atomic gases are analyzed. Our
model incorporates many-body effects through an effective reduction of the
complete microscopic dynamics. Moreover, we simulate the experimental
conditions corresponding to the preparation of the system as a thermal gas and
as a condensate. Some of the experimental findings are clarified. The origin of
the observed dependence of the production efficiency on the frequency,
amplitude, and application time of the magnetic modulation is elucidated. Our
results uncover also the role of the atomic density in the dynamics,
specifically, in the observed saturation of the atom-molecule conversion
process.
