Cl-35 NQR studies of bismuth trichloride

The temperature dependence of the Cl-35 nuclear quadrupole resonance (NQR) frequency and spin lattice relaxation time (T-1) are studied in crystalline BiCl3, in the range 40-300 K. The positive temperature coefficient observed for one of the Cl-35 resonances is explained in terms of the strong intermolecular interactions that exist in this compound. Variation of T-1 with temperature is found to be similar at the chemically inequivalent halogen sites. Semiclassical descriptions based on torsional oscillator dynamics are found to be inadequate for explaining the spin lattice relaxation. T-1(T) data follow an AT(2) + BT3 type behaviour, indicating that the anharmonic nature of the lattice vibrations plays a significant role in determining the temperature dependence of T-1 at high temperatures.