Dynamically assisted tunneling in the impulse regime

We study the enhancement of tunneling through a potential barrier $V(x)$ by a time-dependent electric field with special emphasis on pulse-shaped vector potentials such as Aₓ(t)=A₀/cosh²(ωt). In addition to the known effects of preacceleration and potential deformation already present in the adiabatic regime, as well as energy mixing in analogy to the Franz-Keldysh effect in the nonadiabatic (impulse) regime, the pulse Aₓ(t) can enhance tunneling by ``pushing'' part of the wave function out of the rear end of the barrier. Aside from the natural applications in condensed matter and atomic physics, these findings could be relevant for nuclear fusion, where pulses Aₓ(t) with ω=10.28em0exkeV and peak field strengths of 10¹⁶0.28em0exV/m might enhance tunneling rates significantly.