  Wave-packet scattering from a stationary potential is significantly modified
when the wave-packet is subject to an external time-dependent force during the
interaction. In the semiclassical limit, wave--packet motion is simply
described by Newtonian equations and the external force can, for example,
cancel the potential force making a potential barrier transparent. Here we
consider wave-packet scattering from reflectionless potentials, where in
general the potential becomes reflective when probed by an accelerated
wave-packet. In the particular case of the recently-introduced class of complex
Kramers-Kronig potentials we show that a broad class of time dependent forces
can be applied without inducing any scattering, while there is a breakdown of
the reflectionless property when there is a broadband distribution of initial
particle momentum, involving both positive and negative components.
