O-17 QUADRUPOLE DIPS IN AMMONIUM PERSULFATE

The magnetic field dependence of the H-1 spin-lattice relaxation time in ammonium persulphate shows pronounced minima near the H-1 magnetic resonance frequencies of 1,200 and 2,200 kHz. These are interpreted in terms of a model involving cross-relaxation between H-1 in the NH4+ i on and O-17 in natural abundance in the S2O82- ions, the latter having a much shorter spin-lattice relaxation time. A theoretical analysis o f the shape of the minima is used to derive values for the O-17 quadru pole parameters. This analysis results in best estimate values for the quadrupole coupling constant of 6.75 (+/-0.05) MHz and an asymmetry o f 0.30 (+/-0.02). Such values are indicative of O-H hydrogen bonding a nd suggest the S2O82- ion is not undergoing rapid reorientation at tem peratures below 320 K.