NMR in KH₂PO₄ by Double Resonance Method

Abstract

NMR signals of the potassium in KH₂PO₄ were detected by means of the double resonance technique in the rotating reference frame, and the electric quadrupole coupling constants and associated parameters were determined in the paraelectric (290°K) and ferroelectric (77°K) phases. At 290°K, the electric field gradient at the site of the potassium is axially symmetric (η=0) and |eQq⁄h|=1.68 MHz for K³⁹. At 77°K, |eQq⁄h|=1.479 MHz for K³⁹ and 1.796 MHz for K⁴¹ with the asymmetry parameter η=0.696. The major principal axis of the electric field gradient tensor coincided with the Z(c)-axis in both phases. The values of the electric field gradient were calculated by using point charge model in both paraelectric and ferroelectric phases and compared with the experimental ones.