Deuteron and proton nuclear magnetic resonance studies of crystalline iodic acid

Abstract

The second moment and the linewidth of the proton nuclear magnetic resonance (n.m.r.) spectrum of powdered iodic acid, HIO₃, were measured at 25 and –165°C. The results were the same at both temperatures (second moment = 0.0164 ± 0.0016 mT²; linewidth = 0.361 ± 0.007 mT) indicating that no phase change detectable by n.m.r. techniques occurs in this temperature region. Analysis of the dependence of the quadrupole splitting of the deuteron n.m.r. spectrum on the orientation in the magnetic field of a single crystal of DIO₃ gave the absolute value of the deuteron nuclear quadrupole coupling constant, e²qQ/h, and the orientations of the field gradient tensors associated with deuterons in the four crystallographically equivalent molecules of the unit cell. The value of e²qQ/h is the same, 185 ± 1 kHz, for each deuteron, but the orientations of the field gradient tensors are different. The largest component of the field gradient tensor, V_Z, at each site makes an angle of 2.6° with the O—D bond vector of the DIO₃ molecule.