Cl-35 nuclear quadrupole resonance and the macroscopic superstructure in Hg2Cl2 crystal

A study has been made of the temperature dependences of the chlorine NQR frequency and linewidth in calomel crystals. These dependences show clearly pronounced anomalies in the region of the ferroelastic phase transition. The dynamic and static factors influencing the pattern of these dependences are discussed. A fine structure in the spin echo in the form of beats has been revealed within a narrow temperature interval near the phase transition. This effect is shown to be connected with the formation of a macroscopic heterophase superstructure in the crystal. (C) 1997 American Institute of Physics.