Lineshape analysis and filter difference method for a high intensity time-of-flight inelastic neutron scattering spectrometer

Theoretical Predictions and Single-Crystal Neutron Diffraction and Inelastic Neutron Scattering Studies on the Reaction of Dihydrogen with the Dinuclear Dinitrogen Complex of Zirconium [P2N2]Zr(μ-η2-N2)Zr[P2N2], P2N2 = PhP(CH2SiMe2NSiMe2CH2)2PPh

“…Approximately 1-2 g samples, sealed under helium atmosphere in aluminum sample holders, were used for these experiments. A spectral difference technique 16 was utilized to highlight the vibrational modes of the H atoms in the (µ-H) and (µ-η 2 -NNH) moieties by subtraction of the INS spectrum of the dinitrogen compound {[P2N2]Zr}2(µ-η 2 -N2) from that of {[P2N2]Zr}2(µ-H)(µ-η 2 -N2H). This technique serves to eliminate from the difference spectrum the bands arising from the vibrational modes involving the hydrogen atoms of the [P2N2], provided that their motions are not coupled to those from the (µ-H) and (µ-η 2 -NNH) groups or the coupling is negligible.…”

“…On the basis of the Zr-H-Zr angle θ ) 112°determined by neutron diffraction, and the modified correlation of ν as /ν s vs tan(θ/2) reported by some of us, 16 we can readily assign the peaks at 1053 and 1359 cm -1 to ν s and ν as , respectively.…”

“…While the deformation modes are usually found 16 in the range of 300-700 cm -1 , the strongest peak in our INS at 190 cm -1 must be assigned to the out-of-plane deformation (OP) in view of the very large rms displacement (approximately 0.69 Å) calculated from the anisotropic displacement parameter for the bridging hydride in a direction perpendicular to the Zr-H-Zr plane. This large amplitude suggests an unusually "soft" vibrational frequency and is therefore in good agreement with the strong INS band at 190 cm -1 .…”

Ordering of water in opals with different microstructures

“…Background spectra were collected under identical conditions before each analysis, spectral resolution was 4 cm À1 . Inelastic neutron scattering (INS) spectra were collected on the FDS at the Manuel Lujan, Jr. Neutron Scattering Center (Taylor et al, 1984). The FDS is an inversegeometry instrument for inelastic neutron scattering in energy loss with a fixed final energy determined by the bandpass of Be filters placed ahead of the detectors.…”

Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

“…A cold beryllium reflector-filter will scatter many neutrons with wavelengths less than that of the socalled Bragg edge at 4 Å (5 meV), but it is very nearly transparent above that wavelength. This property of beryllium is frequently exploited as a beam-line filter [13], taking advantage of the change in the scattering cross section from some 6 barns per atom below 4 Å to less than 0.005 barns per atom above that wavelength (cross sections from ENDF/B-VII.0). As the reflector-filter returns neutrons below 4 Å to the moderator and increases the total neutron density therein, the neutrons have a much higher chance of being emitted at wavelengths above the Bragg edge than would otherwise be the case.…”