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The transition-metal ion vanadium in CdTe is studied using electron paramagnetic resonance ͑EPR͒ and photo-EPR. Based on the observation of central hyperfine interaction, the EPR measurements identify two vanadium related defects. They are assigned to V 3ϩ and V 2ϩ , both substitutional for Cd. Whereas V 3ϩ shows the classic isotropic EPR spectrum, the V 2ϩ spectrum features triclinic symmetry caused by a strong Jahn-Teller coupling to both 2 and ⑀ vibronic modes. By means of photo-EPR the V 2ϩ /V 3ϩ -donor level is determined at 0.67 eV below the conduction band.

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Substitutional Ni in synthetic diamonds has been investigated by electron-paramagnetic resonance (EPR) and photo-EPR. The photo-EPR investigation shows that the Ni EPR signal can be diminished by optical illumination, and the threshold energy of 2.47 + 0.02 ev suggests that the acceptor level is located at 3.03 eV above the valence band. The energy dependence of the optical cross section for the electron ionization a. "was determined from an analysis of the EPR transients.

Electrically detected magnetic resonance experiments showing spin dependent recombination in commercial p-n diodes are presented. The observed anisotropy in the g values along with the marked shift from the free electron g-value point to a metal-vacancy complex. Deep level transient spectroscopy reveals the presence of the Pt acceptor level (O/ -) at EC -0.23 eV and the donor level ( + 10) at E, + 0.32 eV in the same device. Calculations of the recombination rates support that spin dependent recombination occurs at the Pt ( + /O) donor level.