Determination of sulfur-33 electric-field-gradient tensors in elemental sulfur by 2D nutation echo NQR

Four 33S quadrupolar frequencies of 33S-enriched elemental sulfur, α-S8, were observed in the range of 23.122–23.280 MHz at the temperature of 140 K. Two-dimensional nutation echo 33S NQR techniques were carried out for each quadrupolar frequency, providing the 33S EFG tensor information; the quadrupolar coupling constant, CQ, of 44.6(5) - 45.7(4) MHz and the asymmetry parameter, ηQ, of 0.30(10) – 0.49(7). Quantum chemical calculations were performed to complete the spectral assignment, and to obtain the 33S EFG tensor orientations with respect to the molecular frame. •33S electric-field-gradient (EFG) tensors could be obtained for elemental sulfur, α-S8.•2D nutation echo NQR experiments were applied at 140 K.•Quantum chemical calculations were performed to complete the spectral assignment. .