Measurements of Chemical-Shift Tensors in KH2PO4 by First-Moment Method

A method is described which allows chemical shifts in solids to be detected to a good accuracy by sharply determining the first moment. The analysis is made by using spin-temperature concepts and it is shown that the chemical-shift tensor can be determined if a single tensor contributes to the spectrum, and the average if more than one tensor contributes. Measurements are made in a single crystal of KH 2 PO 4 . The average tensors obtained are axially symmetric about the c axis with σ // =-25.6 ppm and σ ⊥ =-8.3 ppm relative to C 6 H 12 for 1 H(300 K), and with σ // =-1.1 ppm and σ ⊥ =-16.5 ppm relative to 85% H 3 PO 4 for 31 P(77 K). These values are discussed qualitatively. The 19 F chemical shift in CaF 2 is also obtained, and the result is in good agreement with that of pulse train method.