Ammonium ion rotation in ammonium perchlorate as studied by infrared spectroscopy

TLDR: In this article, the infrared spectra of the ND-stretching bands of dilute NH3D+ in NH4ClO4 were studied over the temperature range from 3 K to room temperature.

Abstract: The infrared spectra of the ND‐stretching bands of dilute NH3D+ in NH4ClO4 are presented. The spectra are studied over the temperature range from 3 K to room temperature. At low temperatures, the NH3D+ is preferentially oriented. The extent of the orientation at a given temperature depends on the deuterium concentration and thus on the concentration of NH3D+ ions. As the temperature is raised, the various ND‐stretching bands collapse due to a variety of dephasing processes. At low temperature, the dephasing process is phonon‐assisted tunneling. As the temperature is raised, dephasing is accomplished by interaction among librational states. At still higher temperatures, the bandwidth is due to stochastic motion of the ammonium ions.