17O Quadrupole Dips in Ammonium Persulphate

Abstract

Abstract The magnetic field dependence of the 1H spin-lattice relaxation time in ammonium persulphate shows pronounced minima near the 1H magnetic resonance frequencies of 1,200 and 2,200 kHz. These are interpreted in terms of a model involving cross-relaxation between 1H in the NH4 ion and 17O in natural abundance in the S2O2- 8 ions, the latter having a much shorter spin-lattice relaxation time. A theoretical analysis of the shape of the minima is used to derive values for the 17O quadrupole parameters. This analysis results in best estimate values for the quadrupole coupling constant of 6.75 (± 0.05) MHz and an asymmetry of 0.30 (± 0.02). Such values are indicative o f O-H hydrogen bonding and suggest the S2O2- 8 ion is not undergoing rapid reorientation at temperatures below 320 K.