Anomalous neutron Compton scattering cross sections in niobium and palladium hydrides

Abstract

The neutron scattering cross sections for hydrogen (H) and deuterium (D) in two metal hydrides have been studied in the Compton (or deep inelastic) scattering regime. Strongly reduced H cross sections were observed in both hydrides. This anomaly was found to depend on the characteristic scattering time, which is a function of the scattering angle and varies from about 0.1 to 1.5 fs in the present experiments. For times longer than 0.6 fs the H cross sections approached the normal, tabulated value. A smaller anomaly was observed for the D cross sections. Our experiments indicate that these, and similar anomalies earlier reported for H/D cross section ratios in water and organic compounds like polymers, amphiphiles, and organic liquids, are caused by very short-lived protonic (deuteronic) quantum correlations---which may also involve electronic degrees of freedom---of neighboring hydrogen atoms in condensed media. The neutron wavelengths are much smaller than the interparticle distances in these experiments. Still, with the support from recent calculations of neutron cross sections for quantum entangled pairs we propose that the anomalies can be explained by the fact that adjacent protons and/or deuterons in the hydrides cannot be considered as individual scattering objects. Entanglement will then modify the cross sections, for scattering times not significantly longer than the decoherence time. Possible mechanisms behind this entanglement and its decoherence are shortly described.