Nuclear Magnetic Resonance Studies of Dislocations in NaI and KI

Intensity anomalies have been found in the nuclear magnetic resonance of I127 in NaI and KI single crystals when the magnetic field is along a [1,0,0] type direction. The intensity enhancement in these cases indicates a collapse of the satellite transitions (m → m − 1, m ≠ ½) into the central transition (m = ½ → m = −½). It is concluded that the crystals contain edge and/or screw dislocations which are preferentially oriented along [1,1,0] and [1,0,0] type directions, respectively. The degree of orientation is greater in NaI than in KI. These studies afford an explanation of anomalous resonance line widths reported for NaI by other observers.