  We investigate the response of superfluid Fermi gases to rapid changes of the
three-dimensional s-wave scattering length a by solving the time-dependent
Bogoliubov-de Gennes equations. In general the magnitude of the order parameter
|\Delta| performs oscillations, which are sometimes called the "Higgs" mode,
with the angular frequency 2 \Delta_{gap}/ \hbar, where \Delta_{gap} is the gap
in the spectrum of fermionic excitations. Firstly, we excite the oscillations
with a linear ramp of 1/a and study the evolution of |\Delta|. Secondly, we
continously drive the system with a sinusoidal modulation of 1/a. In the first
case, the oscillations in |\Delta| damp according to a power law. In the second
case, the continued driving causes revivals in the oscillations. In both cases,
the excitation of the oscillations causes a reduction in the time-averaged
value of |\Delta|. We propose two experimental protocols, based around the two
approaches, to measure the frequency and damping of the oscillations, and hence
\Delta_{gap}.
