Knowledge Bank

It has been suggested that the Stark splitting of spectral lines of molecular crystals in an external electric field can be attributed to a molecular electric dipole moment $change1$ interacting with the local electric field. An anisotropic Lorentz field approximation was used to obtain the local field from the macroscopic $field.1,2$. Other $interactions3$ in the crystal can contribute significantly to the Stark splitting, and many of these have been ignored in previous analyses of such Stark effects. By explicitly including, in a self-consistent way, the many contributions that can arise from guest and host dipole-dipole and dipole-electric field interactions, an improved analysis of the Stark splitting in the spectra of a polar impurity isolated in a nonpolar host crystal is obtained in closed $form,4$ within the context of the point dipole approximation. This analysis results in a second rank tensor that couples the molecular dipole moment change to the macroscopic electric field. This tensor will be compared with that obtained from the Lorentz local field analysis.