Badanie ekranowania magnetycznego jąder [23]Na w związkach typu NaXO[3] metodą magnetycznego rezonansu jądrowego

Abstract

The magnetic shielding of [23]Na nuclei in NaNO[3], NaClO[3], NaBrO[3] was investigated theoretically and experimentally. The theory of the magnetic shielding based on the perturbation theory approach of Ramsey was used. The overlapping-ion model proposed by Kondo and Yamashita to explain the magnetic shielding of nuclei is extended to derive an expression for the shielding tensor in terms of all the important one- and two-center integrals in compounds being investigated. Single crystals of NaNO[3], NaClO[3], NaBrO[3] were investigated experimentally by continuous wave NMR technique. From the shift of the central line of [23]Na triplet, which has been measured as a function of the crystal orientation, the sodium shielding tensors were found for studied compounds. The shielding appears isotropic in sodium nitrate and anisotropic in chlorate and bromate salts. The anisotropies are 12[+]-1 and 17[+]-1 ppm respectively. No agreement between the experiment and the Kondo and Yamashita model was obtained.