ENDOR determination of the ?-deuterium quadrupole tensor in the · CD(COO-)2 radical in a single crystal

The hyperfine and quadrupolar tensors of the ?-deuteron in the ·CD(COO-)2 radical trapped in a single crystal of KH malonate have been determined by ENDOR spectroscopy. Two principal axes of the quadrupolar tensor do not coincide with those of the dipolar tensor. The quadrupole coupling constant is 173 ± 2 kHz, and the asymmetry parameter 0.053 ± 0.028. The ENDOR spectrum of the weakly coupled deuterons corresponding to the ?MI = ±2 transitions is discussed.