On the 75As nmr spectrum in paraelectric NH4H2AsO4

Abstract
The angular dependence of the 75As nmr frequencies and line widths in the paraelectric phase of NH4H2AsO4 fits the pattern established by the ferroelectric KDP-type arsenates. However, the temperature dependence of both line-widths and quadrupole frequency deviates from the ferroelectric pattern near the transition temperature. These deviations are attributed to the different nature of the ADA transition and the presence of two low-frequency modes respectively.