Hg IONS IN KHzP04-TYPE LATTICES: NOVEL SUPERHYPERFINE INTERACTIONS AND 199Hg/20'Hg HYPERFINE ANOMALY

Unlike earlier used paramagnetic probes for KH2P0,-type lattices, the Hg ' ( 6 s ' ) ions exhibit superhyperfine couplings to 4 and 'O'Hg+ (I = 3 / 2) hyperfine transitions yield a new value for the 199Hg/201Hg hyperfine anomaly, a difficult to measure but theoretically important parameter. Evidence is obtained for low symmetry excitations in the high temperature phases of NH4H2P04 and ND,D2P0,, of significance for the development of new theoretical models. 'P nuclei. Detailed computer simulations of 199Hgf (I = 1/2) I