Temperature Dependence of Quadrupole Resonance Frequencies under Constant Pressure

Abstract

The theory of the temperature dependence of pure quadrupole frequencies under constant volume conditions is modified when constant pressure conditions apply. For the case of molecular crystals the first and second derivatives of frequency with respect to temperature have been calculated assuming that (i) the quadrupole coupling constant is independent of volume, and (ii) the lattice frequencies vary linearly with temperature. These derivatives have been evaluated experimentally for the α phase of p-dichlorobenzene, and comparisons made with the theory; good agreement with previous work on the pressure dependence of quadrupole frequencies is obtained.