Tunneling of slow quantum packets through the high Coulomb barrier
  We study the tunneling of slow quantum packets through a high Coulomb barrier. We show that the transmission coefficient can be quite different from the standard expression obtained in the plane wave (WKB) approximation (and larger by many orders of magnitude), even if the momentum dispersion is much smaller than the mean value of the momentum. 
A.V. Dodonov and V.V. Dodonov
quant-ph