Neutron scattering studies on the vibrational excitations and the structure of ordered niobium hydrides: the   phases

Abstract

Neutron vibrational spectroscopy and neutron diffraction have been used to study the optical hydrogen vibrations in and the structure of ordered niobium hydrides NbH x and deuterides NbD x in the concentration range 0.73 < x < 1.0 and at temperatures between 13 and 250 K. The measurements performed at temperatures above 200 K confirm the established model of the β phase. Neutron diffraction data collected in the regime of the λ phases (T < 200 K, 0.73 < x < 1.0) show that the structure for x < 0.85 is made up of microdomains with β phase structure. Neutron vibrational spectra display up to three families of peaks that can be assigned to three different hydrogen sites: an undisturbed tetrahedral site within the microdomains and two strongly disturbed tetrahedral sites within two different kinds of microdomain boundaries. Incommensurately modulated phases probably exist in this concentration range. For hydrogen concentrations around x ≈ 0.85 there is evidence for a change of symmetry of the basic cell as well as a change of the modulation at even higher concentrations. In the range of the γ phase at x ≈ 0.9, strong isotopic effects occur. The results give new insights into the phase diagram.

Ultra low momentum neutron catalyzed nuclear reactions on metallic hydride surfaces

“…For a highly loaded hydride, there will be a full proton layer on the hydride surface. The frequency scale Ω of oscillating surface protons may be computed on the basis of neutron scattering data [15,16]. The electric field scale in Eq.…”

Electron mass shift in nonthermal systems

“…The estimates that result from this approach lead to estimates for the dressed mass that can be enormous. According to their Equation (20), they find…”

“…If we adopt a high value for the oscillation frequency from neutron scattering measurements in NbH [20], wherehω ∼ 100 meV, and a large estimate for the proton range of 1Å, the resulting ratio of the proton velocity to the speed of light is on the order of…”

“…If we assume as discussed above that the relative level of fluctuations are the same for longitudinal and transverse fields, then we need an estimate of the proton velocity to complete the estimate. If we adopt a high value for the oscillation frequency from neutron scattering measurements in NbH [20], where hω ∼ 100 meV, and a large estimate for the proton range of 1 Å, the resulting ratio of the proton velocity to the speed of light is on the order of…”