Resonances in the one-dimensional Dirac equation in the presence of a   point interaction and a constant electric field
  We show that the energy spectrum of the one-dimensional Dirac equation in the presence of a spatial confining point interaction exhibits a resonant behavior when one includes a weak electric field. After solving the Dirac equation in terms of parabolic cylinder functions and showing explicitly how the resonant behavior depends on the sign and strength of the electric field, we derive an approximate expression for the value of the resonance energy in terms of the electric field and delta interaction strength. 
Luis Gonzalez-Diaz, Victor M. Villalba