  We numerically investigate the temporal behavior and the structure of
longitudinal momentum spectrum and the field polarity effect on pair production
in pulsed electric fields in scalar quantum electrodynamics (QED). Using the
evolution operator expressed in terms of the particle and antiparticle
operators, we find the exact quantum states under the influence of electric
pulses and measure the number of pairs of the Minkowski particle and
antiparticle. The number of pairs, depending on the configuration of electric
pulses, exhibits rich structures in the longitudinal momentum spectrum and
undergoes diverse dynamical behaviors at the onset of the interaction but
always either converges to a momentum-dependent constant or oscillates around a
momentum-dependent time average after the completion of fields.
