Molecular Neutron Spectroscopy: Experiment and Ab Initio Methods

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In this project supported by the Experimental Physical Chemistry Program of the Chemistry Division, Hudson will use inelastic incoherent neutron scattering (IINS) spectroscopy to investigate low frequency motions of hydrogen atoms in polycrystalline samples. Comparisons of theory with experiment will be carried out to test the reliability of ab-initio methods by examining their ability to produce accurate eigenvectors for hydrogen atom motions in terms of the contribution of H-atom motion to particular normal modes. Molecules to be studies include those for which (a) empirical or ab-initio methods are expected to fail; (b) experimental analysis of vibrational spectrum is ambiguous; (c) vibrations have not previously detected using optical methods; and (d) the molecule exhibits strong intermolecular interactions. Hudson proposes to use the ISIS pulsed neutron spallation source at the Rutherford Appleton Lab (RAL) in England.The studies proposed here are crucial to understanding a wide variety of fundamental processes in the condensed phase, including the mechanisms by which energy flows in biological molecules. The technique of neutron scattering spectroscopy currently provides the most straightforward method for addressing such questions. As a result of the outcomes of this project, more scientists in the United States can be expected to become involved in work with neutron sources.