The bound coherent neutron scattering lengths of the oxygen isotopes

Fischer, Henry E.; Simonson, J.M.; Neuefeind, Jöerg C.; Lemmel, Hartmut; Rauch, H.; Zeidler, Anita; Salmon, Philip S.

doi:10.1088/0953-8984/24/50/505105

Cited by 12 publications

(12 citation statements)

References 27 publications

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“…10,20−22 Here, we use KNO 3 (in D 2 O) solution as a representative case, using two different substitutions of nitrogen ( nat N/ 15 N) and oxygen ( nat O/ 18 O n ) isotopes on N and O n sites of the NO 3 − anion. This is the first NDIS experiment involving oxygen isotopes on a solute, since it has only recently been discovered that the scattering-length contrast between nat O and 18 O is 0.204(3) fm, 23 nearly 6 times greater than the previously accepted value by Sears et al, 24 and thus sufficient for this type of study. More than just new NDIS data, we use a theoretical approach previously developed but never applied 25 and compare our measurements to those predicted by classical MD simulations.…”

Section: Introductionmentioning

confidence: 65%

“…A combined analysis of NDIS data based on atomistic simulations has only recently been defined, raising the possibility of using this technique to evaluate and parametrize computational models quantitatively; examples include salts in null or HDO water, − nat Ca/ 44 Ca of CaCl 2 –D 2 O solutions, , and anions such as 14 N/ 15 N and 35 Cl/ 37 Cl. − The potential of the NDIS approach to offer an experimental measure of the atomic-scale structure unavailable by other means is highly valuable. ,− Here, we use KNO 3 (in D 2 O) solution as a representative case, using two different substitutions of nitrogen ( nat N/ 15 N) and oxygen ( nat O/ 18 O n ) isotopes on N and O n sites of the NO 3 – anion. This is the first NDIS experiment involving oxygen isotopes on a solute, since it has only recently been discovered that the scattering-length contrast between nat O and 18 O is 0.204(3) fm, nearly 6 times greater than the previously accepted value by Sears et al, and thus sufficient for this type of study. More than just new NDIS data, we use a theoretical approach previously developed but never applied and compare our measurements to those predicted by classical MD simulations.…”

Section: Introductionmentioning

confidence: 65%

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Decoding Oxyanion Aqueous Solvation Structure: A Potassium Nitrate Example at Saturation

et al. 2018

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The ability to probe the structure of a salt solution at the atomic scale is fundamentally important for our understanding of many chemical reactions and their mechanisms. The capability of neutron diffraction to "see" hydrogen (or deuterium) and other light isotopes is exceptional for resolving the structural complexity around the dissolved solutes in aqueous electrolytes. We have made measurements using oxygen isotopes on aqueous nitrate to reveal a small hydrogen-bonded water coordination number (3.9 ± 1.2) around a nitrate oxyanion. This is compared to estimates made using the existing method of nitrogen isotope substitution and those of computational simulations (>5-6 water molecules). The low water coordination number, combined with a comparison to classical molecular dynamics simulations, suggests that ion-pair formation is significant. This insight demonstrates the utility of experimental diffraction data for benchmarking atomistic computer simulations, enabling the development of more accurate intermolecular potentials.

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Section: Introductionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 65%

Decoding Oxyanion Aqueous Solvation Structure: A Potassium Nitrate Example at Saturation

et al. 2018

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“…A key property of neutron diffraction is that the coherent scattering length b c depends on the isotope. The accepted coherent scattering lengths ( b c ) for O and H (data from ref , with the exception of 18 O) given in Table demonstrate the large difference between 1 H and D ( 2 H), as well as the small, but usable difference between 16 O and 18 O.…”

Section: Water Structure From X-ray and Neutron Diffractionmentioning

confidence: 85%

X-ray and Neutron Scattering of Water

et al. 2016

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International audienceThis review article focuses on the most recent advances in X-ray and neutron scattering studies of water structure, from ambient temperature to the deeply supercooled and amorphous states, and of water diffusive and collective dynamics, in disparate thermodynamic conditions and environments. In particular, the ability to measure X-ray and neutron diffraction of water with unprecedented high accuracy in an extended range of momentum transfers has allowed the derivation of detailed O–O pair correlation functions. A panorama of the diffusive dynamics of water in a wide range of temperatures (from 400 K down to supercooled water) and pressures (from ambient up to multiple gigapascals) is presented. The recent results obtained by quasi-elastic neutron scattering under high pressure are compared with the existing data from nuclear magnetic resonance, dielectric and infrared measurements, and modeling. A detailed description of the vibrational dynamics of water as measured by inelastic neutron scattering is presented. The dependence of the water vibrational density of states on temperature and pressure, and in the presence of biological molecules, is discussed. Results about the collective dynamics of water and its dispersion curves as measured by coherent inelastic neutron scattering and inelastic X-ray scattering in different thermodynamic conditions are reported

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“…7,8 To investigate the possibility of using oxygen as a site specific structural probe in neutron diffraction experiments, the sensitive technique of neutron interferometry 215 has recently been applied to measure the coherent scattering length values of the isotopes 17 O and 18 O relative to oxygen of natural isotopic abundance nat O. 216 The measured values of b17 O = 5.867(4) and b18 O = 6.009(5) fm give a factor of C6 increase in the scattering length contrast between 18 O and nat O by comparison with standard tabulations. 217,218 These results encouraged Zeidler et al [21][22][23] to make the first application of the method of oxygen NDIS to measure the structure of light (H 2 O) versus heavy (D 2 O) water to investigate the role played by nuclear quantum effects, such as zero point energy and tunnelling, on water's hydrogen bonded network.…”

Section: Glasses At High-pressures: Mechanisms Of Density-driven Netw...mentioning

confidence: 99%

Identifying and characterising the different structural length scales in liquids and glasses: an experimental approach

Salmon

Zeidler

2013

Phys. Chem. Chem. Phys.

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The structure of several network-forming liquids and glasses is considered, where a focus is placed on the detailed information that is made available by using the method of neutron diffraction with isotope substitution (NDIS). In the case of binary network glass-forming materials with the MX 2 stoichiometry (e.g. GeO 2 , GeSe 2 , ZnCl 2 ), two different length scales at distances greater than the nearest-neighbour distance manifest themselves by peaks in the measured diffraction patterns. The network properties are influenced by a competition between the ordering on these ''intermediate'' and ''extended'' length scales, which can be manipulated by changing the chemical identity of the atomic constituents or by varying state parameters such as the temperature and pressure. The extended-range ordering, which describes the decay of the pair-correlation functions at large-r, can be represented by making a pole analysis of the Ornstein-Zernike equations, an approach that can also be used to describe the large-r behaviour of the pair-correlation functions for liquid and amorphous metals where packing constraints are important. The first applications are then described of the NDIS method to measure the detailed structure of aerodynamically-levitated laser-heated droplets of ''fragile'' glass-forming liquid oxides (CaAl 2 O 4 and CaSiO 3 ) at high-temperatures (B2000 K) and the structure of a ''strong'' network-forming glass (GeO 2 ) under pressures ranging from ambient to B8 GPa. The high-temperature experiments show structural changes on multiple length scales when the oxides are vitrified. The high-pressure experiment offers insight into the density-driven mechanisms of network collapse in GeO 2 glass, and parallels are drawn with the high-pressure behaviour of silica glass. Finally, the hydrogen-bonded network of water is considered, where the first application of the method of oxygen NDIS is used to measure the structures of light versus heavy water and a difference of C0.5% is found between the O-D and O-H intra-molecular bond lengths. The experimental data are best matched by using path integral molecular dynamics simulations with a flexible anharmonic water model, and the results support a competing quantum effects model for water in which its structural and dynamical properties are governed by an offset between intra-molecular and inter-molecular quantum contributions.

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The bound coherent neutron scattering lengths of the oxygen isotopes

Cited by 12 publications

References 27 publications

Decoding Oxyanion Aqueous Solvation Structure: A Potassium Nitrate Example at Saturation

Decoding Oxyanion Aqueous Solvation Structure: A Potassium Nitrate Example at Saturation

X-ray and Neutron Scattering of Water

Identifying and characterising the different structural length scales in liquids and glasses: an experimental approach

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