Positive-energy spectra of atomic hydrogen in a magnetic field with an adiabatic-basis-expansion method

The problem of photoionization of atomic hydrogen in a white-dwarf-strength magnetic field is revisited to understand the existing discrepancies in the positive-energy spectra obtained by a variety of theoretical approaches reported in the literature. Oscillator strengths for photoionization are calculated with the adiabatic-basis-expansion method developed by Mota-Furtado and O'Mahony \[Phys. Rev. A {\bf 76}, 053405 (2007)\]. A comparative study is performed between the adiabatic-basis-expansion method and our previously developed coupled-channel theory \[Phys. Rev. A {\bf 94}, 033422 (2016)\]. A detailed analysis of the positive-energy spectra obtained here and those from other theoretical approaches shows that the adiabatic-basis-expansion method can produce more accurate positive-energy spectra than other reported approaches for low field strengths.