Optical detection of magnetic resonance is reported for isolated interstitial ${\mathrm{Zr}}_1^{+}$ in ZnSe produced by 2.5-MeV electron irradiation at 4.2 K. It is detected as a reduction of the distant-donor–to–Frenkel-pair recombination luminescence at 625 nm. Resolved hyperfine interaction with the central zinc ion and two shells of Se neighbors reveals a highly localized ‘‘deep’’ state for the paramagnetic electron. It is stable only to ∼220 K.

• Received 29 December 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.1486