  Numerical estimates for pair production from vacuum in the presence of strong
electromagnetic fields are derived, for two experimental schemes : the First
concerns a laser based X-FEL and the other imitates the E144 experiment. The
approximation adopted in this work is that of two level multiphoton on
resonance. Utilizing achievable values of laser beam parameters, an
enhancedproduction efficiency of up to 10^11 and 10^15 pairs can be obtained,
for the two schemes respectively.
