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Anomalous neutron Compton scattering cross sections in ammonium hexachlorometallates
M Krzystyniak1, C A Chatzidimitriou-Dreismann, M Lerch
1Institute of Chemistry, Technical University of Berlin, Sekretariat C 2, Strasse des 17, Juni 135, D-10623 Berlin, Germany. krzystyniak@chem.tu-berlin.de
The Journal of Chemical Physics
|April 7, 2007
Summary
Neutron Compton scattering revealed anomalous proton behavior in ammonium metallates. This proton-electron decoherence effect depends on scattering angle, suggesting localized proton environments influence neutron scattering intensity.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Chemistry
Background:
- Ammonium metallates, such as ammonium hexachloropalladate and ammonium hexachlorotellurate, are crystalline compounds.
- Proton dynamics in solids can be influenced by their local electronic environment.
- Neutron Compton scattering is a technique sensitive to the momentum distribution of light nuclei like protons.
Purpose of the Study:
- To investigate the role of the proton's electronic environment on neutron scattering intensity anomalies.
- To quantify the reduction factor of neutron scattering intensities in ammonium metallates.
- To explore the relationship between scattering angle and anomalous neutron scattering effects.
Main Methods:
- Neutron Compton scattering experiments were conducted on ammonium hexachloropalladate ((NH4)2PdCl6) and ammonium hexachlorotellurate ((NH4)2TeCl6) samples.
- Measurements of neutron scattering intensity reduction factors were performed at various scattering angles.
- Proton momentum distributions were analyzed to determine their widths.
Main Results:
- A reduction factor smaller than unity was observed in both samples, indicating anomalous neutron Compton scattering from protons.
- The observed anomaly decreased with decreasing scattering angle and vanished at the lowest scattering angle (longest scattering time).
- The angular dependence of the anomaly and the widths of proton momentum distributions were similar in both metallates, suggesting proton dynamics are decoupled from the anion sublattice.
Conclusions:
- Proton-electron decoherence processes are hypothesized to be responsible for the observed anomalous neutron scattering.
- The anomaly appears to be linked to the direct electronic environment of ammonium protons, rather than the metal-chlorine bond.
- The findings suggest that localized proton dynamics play a significant role in neutron scattering phenomena in these materials.
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