  We demonstrate that ultrashort pulses carry the possibility for a new regime
of light-matter interaction with nonadiabatic electron processes sensitive to
the envelope-derivative of the light pulse. A standard single pulse with its
two peaks in the derivative separated by the width of the pulse acts in this
regime like a traditional double pulse. The two ensuing nonadiabatic ionization
bursts have slightly different ionization amplitudes. This difference is due to
redistribution of continuum electron energy during the bursts, negligible in
standard photo-ionization. A time-dependent close- coupling approach based on
cycle-averaged potentials in the Kramers-Henneberger reference frame permits a
detailed understanding of light pulse derivative-driven electron dynamics.
