Photoabsorption calculations for the magnetised hydrogen atom in the quasi-Landau region

For a hydrogen atom in a uniform magnetic field, wavefunctions and oscillator strengths for bound states are calculated in a region reaching far into the quasi-Landau regime. At the zero-field threshold quasi-Landau photoabsorption peaks are due to groups of individual states which have large amplitudes at small electron-atom separations, but which are not localised around the plane perpendicular to the field and cannot be related diabatically to low-field states. However, in going from the low-field region to the quasi-Landau region the oscillator strengths closely follow trajectories obtained by naively extrapolating the behavior of the low-field K = O states. (author)