Nuclear Quadrupole Resonance in Paramagnetic PrCl3

Abstract

The 35Cl and 37Cl pure quadrupole resonances have been observed in PrCl3. At 4.2°K the frequencies are 4.5667±0.0001 and 3.6001±0.0001 Mc/sec for 35Cl and 37Cl, respectively, and at 77°K they are correspondingly 4.5607±0.0001 and 3.5955±0.0002 Mc/sec. The orientation dependence of the Zeeman split quadrupole resonance frequencies has been measured at 4.2°K and the components of the field gradient tensor determined. The asymmetry parameter η is 0.58±0.02. No evidence of a transition to an ordered state was observed, and it is concluded that PrCl3 remains paramagnetic down to 1.7°K. A shift in the Zeeman frequencies with temperature was found and is attributed to the hyperfine interaction of the Cl nuclei with the Pr electronic ground state. The results are compared with the results of a calculation of the field gradient from a point charge model, and are also discussed in terms of covalent bonding.