Ionization of an Highly Excited Hydrogen atom in parallel Electric and Magnetic fields

In a recent paper, Mitchell {\it et al} [Phys. Rev. Lett. {\bf 92}, 073001 (2004)] investigated the ionization of a classical hydrogen atom in parallel electric and magnetic fields. They reported epistrophic self- similar pulse trains of ionized electrons attributed to the classical chaos induced by the magnetic field. We study hydrogen atom in an excited state with $n\sim 80$ in parallel external fields as an example of an open, chaotic {\it quantum} system in the time domain. We investigate the effect of interference between the outgoing pulse trains which is absent in the classical picture. We look at interference effect as a function of the energy since Schr\"odinger equation does not scale as the classical equations of motion do. We compare and contrast our quantum results with the classical results of Mitchell {\it et al}.