Shakeup processes in the recombination spectra of negatively charged excitons

We report on shakeup processes in the luminescence spectra of a negatively charged exciton (X(-)) at moderate magnetic fields. These processes manifest themselves as a series of low-energy satellite peaks emerging from the negatively charged exciton line. We analyze the dependence of the X(-) energy on magnetic field. We conclude that at magnetic fields above similar to 1 T the X(-) structure can be viewed as an electron at the lowest Landau level bound to an exciton.