Assisted tunneling of a wave packet between square barriers
  The assisted tunneling of a wave packet between square one dimensional barriers is treated analytically. The tunneling rate is calculated exactly for a potential mimicking a constant electric field with arbitrary time dependence. The pole spectrum of the barriers determines the decay time. The tunneling probability is enhanced by the perturbation. The results are exemplified for a simplified model of nuclear $\ds \alpha$ decay. 
G. Kalbermann