Relaxation Modes for Photon-Induced Reorientation of M-Centers in Alkali Halides

Dichroism is induced in potassium chloride crystals containing M‐centers by irradiation at low temperatures with polarized light in the F‐band. This dichroism arises from a reorientation of the M‐centers by ionic motion. The population of the six possible orientations of the M‐center can be described by six relaxation modes, depending on the direction of polarization of the light. Using group theoretical considerations, the relaxation modes are derived for the cases where the polarization of the light is in the [001] and [011] directions.