In addition to the previously reported paramagnetic hole center localized on the chalcogen, a conjugate optically induced electron center localized on an As atom is observed in glassy ${\mathrm{As}}_2$${\mathrm{S}}_3$ and ${\mathrm{As}}_2$${\mathrm{Se}}_3$. The chalcogen center is further identified as a hole localized in a nonbonding $p$ orbital. These optically induced centers are unique to the amorphous phase, and their density saturates at or below ${10}^{17}$ spins/${\mathrm{cm}}^3$.

• Received 20 November 1975

DOI:https://doi.org/10.1103/PhysRevLett.36.543.2