A Python Algorithm to Analyze Inelastic Neutron Scattering Spectra Based on the y-Scale Formalism

Abstract

This paper presents a Python-based algorithm, named INSCorNorm, to correct the inelastic neutron scattering (INS) spectra for both sample and container self-shielding and to normalize the experimental spectral intensity to an absolute physical scale (barn/energy unit) facilitating the comparison with computer simulations and interpretation. The algorithm is benchmarked against INS measurements of ZrH 2 performed on the TOSCA spectrometer at the ISIS Facility. We also apply the algorithm to the INS spectra from L-lysine, a system of broad interest in biology and medicine, and we discuss how corrected INS data provide an experimental benchmark for theoretical calculations of nuclear anisotropic displacement parameters in molecular systems. The total neutron sample cross section to use for the self-shielding corrections is discussed, as well as the best approach to derive experimentally the cross section at the VESUVIO spectrometer, together with the experimental value of the hydrogen nuclear mean kinetic energy, ⟨E k ⟩. The algorithm is made available to the neutron user community within the MANTID software. 45 capabilities have been significantly enhanced following the 46 installation of a neutron guide, 5,6 the upgrade of the beryllium 47 filters, 7 and the ability to exploit the empty pulse resulting from 48 ISIS TS2 operation, giving access to the elastic line and 49 extending the energy transfer range to as low as −3 meV (i.e., 50 the "anti-Stokes" side of the elastic line). 7 Given the large cross 51 section of hydrogen (82.03 barn), the INS technique is 52 particularly suitable to study hydrogenous compounds where 53 the scattering of neutrons is dominated by hydrogen. ZrH 2 is 54 often used as a reference material owing to its simple, 55 reproducible, and well-known behavior: it allows a full 56 assignment in terms of fundamental, overtone, 8 and combina-57 tion modes. 9 58 INS experimental results can be readily compared with the 59 INS spectra generated from single-molecule or periodic DFT 60 calculations. However, it is rare to express the experimental 61 data on an absolute intensity scale. The current practice is to 62 scale the calculated spectrum to match the experimental one. If 63 the experimental data were on an absolute scale, this would 64 remove an arbitrary procedure. The use of an absolute scale

Thermal neutron cross sections of amino acids from average contributions of functional groups

“…In particular, the application of the script developed here would be suitable for the reduction and normalization algorithm presented in Ref. 91 . While the agreement between our calculations and the experimental results is a powerful benchmark of our algorithm, we performed additional comparisons applying the LEAPR module of NJOY2016 17 to our VDoS.…”

MWCNT/rGO/natural rubber latex dispersions for innovative, piezo-resistive and cement-based composite sensors

“…The several ller dispersions (described in Table 1) were loaded in 1-mm-thick indium-sealed containers, while mortars were placed as prepared, without the need to grind the samples, with approximate thickness of 2.5 mm. Aluminum is generally used as sample container owing to its low scattering cross section for neutrons [63], thus providing a negligible self-attenuation correction [64].…”

Hydrogen Detection Limits and Instrument Sensitivity of High-Resolution Broadband Neutron Spectrometers

“…TOSCA is a broadband neutron spectrometer optimized for molecular spectroscopy. ,,− It is based on the inverted-geometry configuration for time-of-flight (ToF) spectrometers, which is particularly suitable for a vibrational spectroscopy instrument on a spallation source because a wide range of energy transfer is required. TOSCA is able to record spectra in a broad spectral range, from −3 to 1000 meV (1 meV = 8 cm –1 ) of energy transfer, and it has high spectral resolution of Δ E / E ∼ 1.25%.…”