ESR of 17O-Labeled PO32− Ion Trapped in a Single Crystal of Na2DPO3·5D2O

The ESR spectrum of an x‐irradiated ¹⁷O‐enriched Na₂DP¹⁷O₃·5D₂O single crystal is reported. The results show unambiguously that the radical formed is PO₃²⁻. The values and directions of the principal components of the ¹⁷O and ³¹P hyperfine tensors were determined and were used to derive values for the atomic‐orbital coefficients in the ${\text{6a}}_1$ molecular orbital containing the odd electron. The relative orientation of the two magnetically inequivalent PO₃²⁻ radicals in the unit cell in deuterated crystals was found to differ markedly from that in the isotopically normal crystal.