Abstract
We continue our study of the optical dephasing of impurities by phonons. The pure dephasing contribution to the homogeneous linewidth is calculated to all orders in the excitation–phonon interaction. We introduce a microscopic model for the pseudolocal phonon spectral density when the impurity is in the ground electronic state. This microscopic model improves upon our previous phenomenological model. The model is applied to several experimental systems—in all cases, the theoretical results provide a reasonably accurate description of the temperature-dependent linewidth with no adjustable parameters.