Showing papers by "J. Mayers published in 2003"

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\char22{}which may also involve electronic degrees of freedom\char22{}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.

Kinetic energy of He atoms in liquid 4He-3He mixtures

Abstract: Deep inelastic neutron scattering measurements on liquid 3 He- 4 He mixtures in the normal phase have been performed on the VESUVIO spectrometer at the ISIS pulsed neutron source at exchanged wave vectors of about q≃1200 A - 1 The neutron Compton profiles J(y) of the mixtures were measured along the T = 196 K isotherm for 3 He concentrations, x, ranging from 01 to 10 at saturated vapor pressures Values of kinetic energies of 3 He and 4 He atoms as a function of x, (x), were extracted from the second moment of J (y) The present determinations of (x) confirm previous experimental findings for both isotopes and, in the case of 3 He, a substantial disagreement with theory is found In particular (x) for the 3 He atoms is found to be independent of concentration yielding a value 3 (x=01)≃12 K, much lower than the value suggested by the most recent theoretical estimates of approximately 19 K

Kinetic energy of He atoms in liquid He-4-He-3 mixtures

Abstract: Kinetic energy of He atoms in liquid He-4-He-3 mixtures. Deep inelastic neutron scattering measurements on liquid He-3- He-4 mixtures in the normal phase have been performed on the VESUVIO spectrometer at the ISIS pulsed neutron source at exchanged wave vectors of about qsimilar or equal to120.0 Angstrom(-1). The neutron Compton profiles J(y) of the mixtures were measured along the T=1.96 K isotherm for He-3 concentrations, x, ranging from 0.1 to 1.0 at saturated vapor pressures. Values of kinetic energies of He-3 and He-4 atoms as a function of x, (x), were extracted from the second moment of J(y). The present determinations of (x) confirm previous experimental findings for both isotopes and, in the case of He-3, a substantial disagreement with theory is found. In particular (x) for the He-3 atoms is found to be independent of concentration yielding a value (3)(x=0.1)similar or equal to12 K, much lower than the value suggested by the most recent theoretical estimates of approximately 19 K.