• defect;
  • diamond;
  • EPR;
  • hydrogen

An electron paramagnetic resonance (EPR) study of synthetic diamond crystals grown at HTHP conditions in the carbonate medium Na2CO3[BOND]CO2[BOND]H2O[BOND]C has revealed a hydrogen-containing center (VOH) along with centers OX1, OX2, and OX3 tentatively associated with oxygen. In the X-band EPR spectra, the forbidden transitions of the center are superimposed on the allowed HFS lines of one hydrogen atom. We have succeeded in analysis of the allowed transitions in Q-band experiments. On the basis of the obtained experimental data a hypothetical model of the center has been proposed as a vacancy–oxygen complex with incorporated hydrogen atom. The occurrence of hydrogen in the studied diamond crystals is supported by the presence of C[BOND]H vibrations in the IR spectra in the range of 3000 cm−1.