Neutron Compton scattering investigation of sodium hydride: from bulk material to encapsulated nanoparticulates in amorphous silica gel.

In this study we utilize neutron Compton scattering (NCS) to determine differences in nuclear momentum distributions in NaH, both as bulk material and encapsulated as nanoscale particles (from 20 to 50 nm in diameter) within an amorphous silica-gel matrix (SiGNaH). In addition, elemental Na dispersed in such a matrix is also studied (SiGNa). Data treatment and fitting of experimental spectra yields comparison of the nuclear Compton profiles and radial momentum distributions for the proton in both bulk NaH and nanoscale SiGNaH, with resultant proton kinetic energies being in agreement with previous inelastic neutron studies of bulk NaH. Slight differences in proton radial momentum distributions for bulk and nanoscale systems are witnessed and discussed. The technique of stoichiometric-fixing is applied to the backscattering spectra of each system in order to examine changes in the Na profile width, and NCS is shown to be sensitive to the chemical environment change of this heavier nucleus. Examination of the Si and O profile widths in the gel samples also supports this method.

[1]  G. L. Squires,et al.  Introduction to the Theory of Thermal Neutron Scattering: Neutron optics , 1978 .

[2]  M. Lerch,et al.  Anomalous neutron Compton scattering cross sections in ammonium hexachlorometallates. , 2007, The Journal of chemical physics.

[3]  P M Platzman,et al.  Anomalous behavior of proton zero point motion in water confined in carbon nanotubes. , 2006, Physical review letters.

[4]  J. Eckert,et al.  Measurement of the 3D Born-Oppenheimer potential of a proton in a hydrogen-bonded system via Deep Inelastic Neutron Scattering: the superprotonic conductor Rb(3)H(SO(4))(2). , 2007, Physical review letters.

[5]  Momentum-distribution spectroscopy using deep inelastic neutron scattering , 1999, cond-mat/9904095.

[6]  R. Cowley,et al.  Anomalous neutron scattering from hydrogen , 2006 .

[7]  J. Mayers,et al.  The measurement of anomalous neutron inelastic cross-sections at electronvolt energy transfers , 2004 .

[8]  A. C. Evans,et al.  The kinetic energy of lithium-7 above and below the martensitic transformation , 1994 .

[9]  M. Zoppi,et al.  Extraction of the density of phonon states in LiH and NaH , 2004 .

[10]  Maciej Krzystyniak,et al.  Short lived protonic quantum entanglement and coupling to the electronic environment in LaH2 and LaH3 , 2005 .

[11]  Roberto Senesi,et al.  Measurement of momentum distribution of lightatoms and molecules in condensed matter systems using inelastic neutron scattering , 2005 .

[12]  S. Billinge,et al.  Structures of alkali metals in silica gel nanopores: new materials for chemical reductions and hydrogen production. , 2007, Journal of the American Chemical Society.

[13]  J. Mayers,et al.  Anomalous Deep Inelastic Neutron Scattering from Liquid H 2 O- D 2 O: Evidence of Nuclear Quantum Entanglement , 1997 .

[14]  C. Chatzidimitriou-Dreismann,et al.  Anomalous neutron scattering and coupling of protons to the environment at different temperatures , 2004 .

[15]  M. Krzystyniak,et al.  Anomalous neutron Compton scattering from molecular hydrogen , 2005 .

[16]  Carla Andreani,et al.  Initial state effects in deep inelastic neutron scattering. , 1989, Physical review. B, Condensed matter.

[17]  Mayers.  Quantum effects in deep inelastic neutron scattering. , 1990, Physical review. B, Condensed matter.

[18]  A. C. Evans,et al.  A deep inelastic neutron scattering study of sodium , 1994 .

[19]  R Senesi,et al.  Changes in the zero-point energy of the protons as the source of the binding energy of water to A-phase DNA. , 2010, Physical review letters.

[20]  Andrew L. Fielding,et al.  Measurement of anisotropies of the kinetic energy and anharmonicity in pyrolytic graphite by neutron Compton scattering , 1998 .

[21]  A. Pietropaolo,et al.  Neutron Compton scattering as a molecular characterization technique: A study on NaHF{sub 2} , 2007 .

[22]  P. Georgiev,et al.  Relevance of the electronic environment for the neutron scattering behavior of protons , 2006 .

[23]  P. Edwards,et al.  Formation of Crystalline Sodium Hydride Nanoparticles Encapsulated Within an Amorphous Framework , 2010 .

[24]  F. Bruni,et al.  Quantum behavior of water protons in protein hydration shell. , 2009, Biophysical journal.

[25]  S. Imberti,et al.  Proton quantum coherence observed in water confined in silica nanopores. , 2007, The Journal of chemical physics.

[26]  Roberto Senesi,et al.  Excess of Proton Mean Kinetic Energy in Supercooled Water , 2008 .