Inelasticity Effect on Neutron Scattering Intensities of the Null-H2O

Abstract

Time-of-flight (TOF) neutron scattering measurements have been carried out for liquid null-H 2 O, in which the average coherent scattering length of hydrogen atoms is zero. In order to determine the inelasticity effect depending on both the scattering angle and the neutron flight path ratio, g ½¼ l s =ðl 0 þ l s Þ; l 0 and l s denote the moderator-sample and sample-detector distances, respectively], neutron scattering measurements have been performed using three neutron spectrometers, HIT-II, RAT, and SWAN, installed at KENS, Tsukuba, Japan. The self-scattering intensity for the null-H 2 O was derived by subtracting the known O-O partial structure factor from the observed scattering cross-section. It has been revealed that the magnitude of the inelasticity distortion involved in the self-scattering term is still significant even at a smaller scattering angle than that expected from the first-order inelasticity correction formulas proposed in the literature. The inelasticity distortion in the self-scattering term is found to be preferably reduced by applying the small flight path ratio. An empirical but useful correction procedure for the inelasticity effect is developed using the self-scattering intensities observed for the null-H 2 O. The present correction procedure is applied to the scattering cross-section observed for aqueous 3 mol% alanine solution which involves 20% H of exchangeable hydrogen atoms, and to the first-order difference function D H (Q) observed for 4 mol% lithium benzoate heavy water solutions in which H/D isotopic substitution has been applied for benzyl-hydrogen atoms within the benzoate ion. The results indicate that the present inelasticity correction procedure works satisfactorily for the scattering intensity from the aqueous solution containing H atoms.

Inelasticity corrections for time-of-flight and fixed wavelength neutron diffraction experiments

“…Recoil corrections for any molecule". The various approaches fall into three main categories: those which derive from the original moment expansion as proposed by Placzek [2], for example [5-11, 13-15, 20, 21, 23], those that use a model for S(Q, ǫ) and integrate this over the relevant path in momentum and energy transfer space, for example [12, 16-19, 22, 25-28], and those that use some form of ad hoc fitting function to remove the single atom scattering, for example [24,29,30].…”

Structure of Highly Concentrated Aqueous Lithium Alaninate Solutions Studied by Neutron Diffraction with 14N/15N, 6Li/7Li, and H/D Isotopic Substitution Methods

“…The inelasticity correction was applied by the use of the observed self-scattering intensities from the liquid null-H 2 O. 15 The first-order difference function, Á X ðQÞ, 16,17 is derived from the numerical difference between scattering cross sections observed for two solutions that are identical except for the scattering length of the nucleus X. The Á X ðQÞ can be written as a linear combination of partial structure factors, a Xj ðQÞ, involving contributions from the X-j pair:…”

The Design of the Neutron Total Scattering Spectrometer for Hydrogenous Materials at J-PARC-JSNS

“…We therefore conclude that the small flight path ratio is more favorable for the accurate measurement of TOF neutron total scattering for hydrogenous materials, except for SANS measurements. The details of the systematic studies of the inelasticity effect on TOF neutron total scattering intensities using null-H 2 O liquid and various TOF spectrometers are described in a separate paper, Kameda et al [8] and on the basis of the studies, the novel inelasticity correction method, using null-H 2 O liquid, for extracting an accurate structure factor S(Q) of hydrogenous material is proposed [8,9].…”

“…In order to obtain detailed information on the effect of the flight path ratio, g, the self scattering intensities of the null-H 2 O ðH=D ¼ 64=36Þ; whose average coherent scattering length for hydrogen is zero, were measured by the use of HIT-II and RAT spectrometers at KENS with the same ambient H 2 O moderator and with the same scattering angle 2u ¼ 308; but with the different values of g [8]. Figure 1 shows the dependence of the self scattering intensity on the value of g. A hump in the scattering intensity appearing at Q , 6 Å 21 in the HIT-II data is much reduced in the RAT data which have been obtained with the smaller values of g. The self-scattering intensity of the RAT data varies more smoothly as a function of Q (.…”