title: Deuteron NMR spectra and relaxation in fully and partly deuterated (NH4)2ZnCl4.
abstract: Deuteron NMR spectra and relaxation were studied at the resonance frequency of 46MHz in polycrystalline fully and partly deuterated (NH(4))(2)ZnCl(4) between 300 and 5K. Spectral components confirm existence of ammonium positions with different potential symmetry, resulting in two- and threefold reorientation of ammonium ions. The temperature dependence of the spin-lattice relaxation rate discloses two time constants in the whole range. The fitting procedure allows the separation into contributions from subsystems of ions in respective potentials. Two relaxation rate maxima are attributed to ions performing threefold uniaxial reorientation at low temperatures. The lower-temperature maximum is observed at T36K. With increasing temperature reorientations about remaining axes start to contribute leading to the other maximum near 100K. The other category of ammonium ions gives rise to the maximum at about 50K. Below this temperature the dominant motion seems to be 180( composite function) reorientations about one twofold axis according to observed spectra. Consistent picture of ion mobility is accomplished for 5%, 30%, 70% and 100% deuterated compounds.
authors.affiliation: H Niewodniczański Institute of Nuclear Physics of PAS, Kraków, Poland.
authors.forename: G
authors.initials: G
authors.lastname: Stoch
authors.forename: E E
authors.initials: EE
authors.lastname: Ylinen
authors.forename: M
authors.initials: M
authors.lastname: Punkkinen
authors.forename: B
authors.initials: B
authors.lastname: Petelenz
authors.forename: A
authors.initials: A
authors.lastname: Birczyński