  We present a grid-free DFT model appropriate to explore the time evolution of
electronic states in a semiconductor nanostructure. The model can be used to
investigate both the linear and the nonlinear response of the system to an
external short-time perturbation in the THz regime. We use the model to study
the effects of impurities on the magneto-spectroscopy of a two-dimensional
electron gas in a nanostructure excited by an intense THz radiation. We do
observe a reduction in the binding energy of the impurity with increasing
excitation strength, and at a finite magnetic field we find a slow onset of
collective spin-oscillations that can be made to vanish with a stronger
excitation.
