Relativistically Enhanced Ionization Rates at Stark-Effect Level Crossings in Hydrogen

Relativistic coupling terms at crossings between hydrogen Stark levels are computed with numerical Stark wave functions. Over a small interval of the electric field at crossings between a slowly and a rapidly ionizing state, the ionization rate of the former is increased. The effect is calculated to be observable with available techniques at more than thirty crossings between two $m_L=0\mathrm{}$ levels in the range 7 to 140 kV/cm, $n=7\mathrm{} \mathrm{to} 16$.