The dimensionality of ammonium reorientation in (NH4)(2)S2O8: the view from neutron spectroscopy

Journal article

Publication Details

Author(s): Prager M, Grimm H, Natkaniec I, Nowak D, Unruh T
Journal: Journal of Physics: Condensed Matter
Publication year: 2008
Volume: 20
Journal issue: 12
ISSN: 0953-8984
eISSN: 1361-648X


The dynamics of the ammonium ion in ammonium persulfate is studied by inelastic neutron scattering at energy transfers between 0.7 mu eV and about 100 meV. NH4+ librational modes are clearly split into four energetically different bands, in agreement with the absence of symmetry at the ammonium site. One strong, one medium and two weak hydrogen bonds from the NH4 ion to neighboring oxygens lead to this unusual potential shape with one dominating overlap matrix elements hi. Therefore the ammonium dynamics seen by neutron tunneling spectroscopy looks like a rotation about a single axis, that of the strongest hydrogen bond. Quasi-elastic scattering up to T = 100 K is dominated by jumps about this specific axis, too. Jumps about the second weak axis modify the quasi-elastic scattering at higher temperature. Results of a previous nuclear magnetic resonance (NMR) quadrupole resonance experiment are consistently interpreted to show the dynamics around the remaining two strong axes. The reduced isotope effect of the lowest librational band is due to a special shape of the potential and not to changes of the hydrogen bond with deuteration.

FAU Authors / FAU Editors

Unruh, Tobias Prof. Dr.
Professur für Nanomaterialcharakterisierung (Streumethoden)

External institutions with authors

Adam Mickiewicz University / Uniwersytet im. Adama Mickiewicza w Poznaniu (UAM)
Forschungszentrum Jülich / Research Centre Jülich (FZJ)
Institute of Nuclear Physics PAN / Instytut Fizyki Jądrowej im. Henryka Niewodniczańskiego PAN

How to cite

Prager, M., Grimm, H., Natkaniec, I., Nowak, D., & Unruh, T. (2008). The dimensionality of ammonium reorientation in (NH4)(2)S2O8: the view from neutron spectroscopy. Journal of Physics: Condensed Matter, 20(12).

Prager, Michael, et al. "The dimensionality of ammonium reorientation in (NH4)(2)S2O8: the view from neutron spectroscopy." Journal of Physics: Condensed Matter 20.12 (2008).


Last updated on 2018-06-08 at 20:23