NMR in KH2PO4 by Double Resonance Method

NMR signals of the potassium in KH 2 PO 4 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 | e Q q / h |=1.68 MHz for K 39 . At 77°K, | e Q q / h |=1.479 MHz for K 39 and 1.796 MHz for K 41 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.