A novel experimental set-up for in operando studies of homogeneous catalyzed reactions under laboratory conditions has been developed and tested. It combines time-resolved X-ray absorption spectroscopy with UV/Vis spectroscopy. The reaction solution is stirred in a vessel and pumped in a circle by a peristaltic free gear-wheel through a measurement cell. The X-ray and UV/Vis beams probe the same sample volume of the cell orthogonally. Reactants can be added to the reaction mixture in the course of the measurements and a defined gas atmosphere can be adjusted up to a pressure of 10 bar. The in situ reduction of cerium(IV) ammonium nitrate to cerium(III) by isopropanol is studied as a test reaction with quick-XANES and UV/Vis measurements with a time resolution of 60 s and 1 s, respectively.

The gas phase of hydrogen fluoride has been investigated by neutron diffraction experiments at three different particle densities. All investigated states are within the liquid-gas coexistence region of hydrogen fluoride. From the obtained diffraction data we deduced information about the local structure of the gas phase, which consists of small agglomerates. This has been expected as liquid hydrogen fluoride forms the strongest hydrogen bonds known. Molecular dynamics simulations with a modified potential have been carried out for all experimentally investigated states. The results confirmed that the size of the formed agglomerates in the gas phase is growing with increasing density of the gas phase.

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Hydrogen Bonding . Liquid Dynamics . Neutron SpectroscopyThe collective motions in liquid deuterium fluoride (DF) have been investigated by neutron scattering motivated by a MD simulation, which predicted an optic-type mode at small momentum transfers. Spectra of the measured longitudinal current correlation function show two modes. The lower frequency one originates from acoustic-type movements. The intensity of the higher frequency excitation can be attributed to an out of phase motion of neighboring DF molecules, an optic-type mode. Both, the frequencies and the intensity distribution in momentum space agree well with the MD simulation. The widths of the experimental spectra exceed the widths from the MD simulation and indicate missing relaxation processes in the simulation.