Ion dynamics in moltmolti melkaltal nitrates

Quasielastic neutron scattering experiments have been performed on simple molten alkali metal nitrates, RbNO3 and LiNO3. The experiments were carried out by the medium resolution inverted geometry spectrometer LAM-40 at KENS neutron scattering facility in Japan. The measured spectra are composed of narrow and broad quasielastic spectra. We assigned that the broad component corresponds to the fast intra-ionic motions in a nitrate ion. From momentum dependence of integrated intensity for this component it is found that the motion of nitrate ions in RbNO3 melt is mainly the librational one centered C3 axis on the ion. On the other hand the intra-ionic motion in LiNo3 is the librational motion cnetered C3 axis on the nitrate ion which amplitude is smaller than in RbNO3 melt. This fact shows that the motion of nitrate ions in LiNO3 is restricted strongly by surrounding cations. (author)