A self-trapped hole ($V_k$ center) has been identified by means of electron paramagnetic resonance in single crystals of ${\mathrm{Rb}}_2$${\mathrm{ZnCl}}_4$ x-irradiated at 77 K. This center presents a broad (∼0.8 eV) absorption band at 385 nm which is anisotropic and σ polarized. The thermal and optical bleaching of the $V_k$ centers has been studied through EPR and optical experiments.

• Received 16 March 1988

DOI:https://doi.org/10.1103/PhysRevB.38.6392