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Articles you may be interested inExperimental and computational studies on collective hydrogen dynamics in ammonia borane: Incoherent inelastic neutron scattering Investigation of structure of liquid 2,2,2 trifluoroethanol: Neutron diffraction, molecular dynamics, and ab initio quantum chemical study Inelastic neutron scattering experiments were performed at intermediate and high momentum transfer, up to 88.2 Å Ϫ1 , to study the temperature dependence of single hydrogen mean kinetic energy in polycrystalline and liquid hydrogen sulphide (H 2 S), in the temperature range 16-206 K. Values of the hydrogen mean kinetic energy were extracted, within the impulse approximation, by fitting to the high momentum transfer data a model response function, obtained from a momentum distribution which is the orientational average of a multivariate Gaussian function. The extracted kinetic energies are compared with a harmonic model for the vibrational and roto-translational dynamics. The model makes use of the hydrogen-projected density of states worked out from intermediate momentum transfer data, as well as of optical frequencies determined from Raman and infrared ͑IR͒ spectroscopy. A fairly good agreement is obtained in the whole temperature range, while noticeably lower values for the kinetic energy are found if a single atom momentum distribution of isotropic Gaussian shape is assumed in the model response function.

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The structure in aqueous solutions of the hydrated selenate and chromated ions SeO 2-and CrO 2-have been derived from X-ray and neutron diffraction measurements using CrO 2-as an isomorphous substitute for SeO 2-. The Se(Cr)-O bond lengths are 1.63 _+ 0.02A and do not differ from those found in crystal structure.A well defined hydration shell of about 12 water molecules surrounds the XO 2-ions at a Se(Cr)-H:O distance of 3-96 A. The diffraction results indicate a geometrical orientation of the water molecule around the tetrahedral anions very similar to that one found in the case of simple anions such as CI-, with Se(Cr)-D distances of 3.25 and 4.4 A and with a Se(Cr)-O distance of 3.96 A.