Autoionizing states of the hydrogen atom in strong magnetic fields

For a hydrogen atom in a uniform magnetic field in the range $B\approx 2.35\times {10}^8-2.35\mathrm{}\times {10}^9$ G we have calculated the energies and widths of resonant states which can autoionize by decay of a Landau excitation. The autoionization widths are quite large with some lifetimes as short as ${10}^{-15\mathrm{}}$ sec. The widths decrease with increasing azimuthal quantum number $\mathrm{}\left|m\right|\mathrm{}$, hydrogenic quantum number, or magnetic field strength. With decreasing field strength the lower resonances approach the ionization threshold which they cross with finite width and a pseudoresonance structure of finite width persists below threshold in the quantum defects of the bound states. Because of the finite widths, there are no approximate level crossings as these resonances cross the ionization threshold.