Destabilization of dark states and optical spectroscopy in Zeeman-degenerate atomic systems

We present a general discussion of the techniques of destabilizing dark states in laser-driven atoms with either a magnetic field or modulated laser polarization. We show that the photon-scattering rate is maximized at a particular evolution rate of the dark state. We also find that the atomic-resonance curve is significantly broadened when the evolution rate is far from this optimum value. These results are illustrated with detailed examples of destabilizing dark states in some commonly trapped ions and supported by insights derived from numerical calculations and simple theoretical models.