Neutron scattering by inhomogenous distribution of proton polarization produced by the dynamic nuclear polarization

1987 ◽  
Vol 35 (1-4) ◽  
pp. 1071-1074
Author(s):  
Y. Masuda
Keyword(s):  
Neutron Scattering ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Proton Polarization

Inhomogeneous dynamic nuclear polarization of protons in a lamella-forming diblock copolymer investigated by a small-angle neutron scattering method

2011 ◽  
Vol 44 (3) ◽  
pp. 503-513 ◽  
Author(s):  
Yohei Noda ◽  
Takayuki Kumada ◽  
Takeji Hashimoto ◽  
Satoshi Koizumi
Keyword(s):  
Neutron Scattering ◽  
Diblock Copolymer ◽  
Dynamic Nuclear Polarization ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Second Order ◽  
Third Order ◽  
Proton Polarization

By combining two methods of selective doping of paramagnetic species into a microdomain and small-angle neutron scattering (SANS), thespatially inhomogeneous proton polarizationcreated by dynamic nuclear polarization (DNP) has been precisely evaluated. A lamella-forming diblock copolymer composed of polystyrene (PS) and polyisoprene (PI) block chains (PS-b-PI) was employed, the SANS profile of which clearly shows scattering peaks up to the third order due to interlamellar interference. As a source of electron spin for DNP, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) was doped into one or other of the microdomains; samples with PS or PI microdomains selectively doped with TEMPO are designated PS.-b-PI and PS-b-PI., respectively. The SANS intensity at the first- and third-order peaks is well reproduced by assuming that the proton polarization is homogeneous throughout the sample, but that at the second-order peak cannot be explained by this assumption. This anomaly regarding the second-order peak was successfully explained by a model postulating that proton polarization in a doped microdomain decreases with increasing distance from the interface with a neighbouring doped microdomain. The decrease in proton polarization at the centre of a doped microdomain was estimated to be 0.07 (2) for PS-b-PI.and 0.05 (1) for PS.-b-PI, relative to constant proton polarization in a doped microdomain. The inhomogeneous proton polarization results from two competing dynamic processes,i.e.spin diffusion from doped to undoped microdomains, and spin lattice relaxation occurring on the pathway of proton spin diffusion.

scholarly journals Contrast variation by dynamic nuclear polarization and time-of-flight small-angle neutron scattering. I. Application to industrial multi-component nanocomposites

2016 ◽  
Vol 49 (6) ◽  
pp. 2036-2045 ◽  
Author(s):  
Yohei Noda ◽  
Satoshi Koizumi ◽  
Tomomi Masui ◽  
Ryo Mashita ◽  
Hiroyuki Kishimoto ◽  
...  
Keyword(s):  
Form Factor ◽  
Binary Mixture ◽  
Neutron Scattering ◽  
Dynamic Nuclear Polarization ◽  
Small Angle ◽  
Ternary Mixture ◽  
Small Angle Neutron Scattering ◽  
Nuclear Polarization ◽  
Scattering Function ◽  
Contrast Variation

Dynamic nuclear polarization (DNP) at low temperature (1.2 K) and high magnetic field (3.3 T) was applied to a contrast variation study in small-angle neutron scattering (SANS) focusing on industrial rubber materials. By varying the scattering contrast by DNP, time-of-flight SANS profiles were obtained at the pulsed neutron source of the Japan Proton Accelerator Research Complex (J-PARC). The concentration of a small organic molecule, (2,2,6,6-tetramethylpiperidine-1-yl)oxy (TEMPO), was carefully controlled by a doping method using vapour sorption into the rubber specimens. With the assistance of microwave irradiation (94 GHz), almost full polarization of the paramagnetic electronic spin of TEMPO was transferred to the spin state of hydrogen (protons) in the rubber materials to obtain a high proton spin polarization (PH). The following samples were prepared: (i) a binary mixture of styrene–butadiene random copolymer (SBR) with silica particles (SBR/SP); and (ii) a ternary mixture of SBR with silica and carbon black particles (SBR/SP/CP). For the binary mixture (SBR/SP), the intensity of SANS significantly increased or decreased while keeping itsqdependence forPH= −35% orPH= 40%, respectively. Theqbehaviour of SANS for the SBR/SP mixture can be reproduced using the form factor of a spherical particle. The intensity at lowq(∼0.01 Å−1) varied as a quadratic function ofPHand indicated a minimum value atPH= 30%, which can be explained by the scattering contrast between SP and SBR. The scattering intensity at highq(∼0.3 Å−1) decreased with increasingPH, which is attributed to the incoherent scattering from hydrogen. For the ternary mixture (SBR/SP/CP), theqbehaviour of SANS was varied by changingPH. AtPH= −35%, the scattering maxima originating from the form factor of SP prevailed, whereas atPH= 29% andPH= 38%, the scattering maxima disappeared. After decomposition of the total SANS according to inverse matrix calculations, the partial scattering functions were obtained. The partial scattering function obtained for SP was well reproduced by a spherical form factor and matched the SANS profile for the SBR/SP mixture. The partial scattering function for CP exhibited surface fractal behaviour according toq−3.6, which is consistent with the results for the SBR/CP mixture.

scholarly journals Polarization analysis in neutron small-angle scattering with a novel triplet dynamic nuclear polarization spin filter

2015 ◽  
Vol 48 (5) ◽  
pp. 1514-1521 ◽  
Author(s):  
N. Niketic ◽  
B. van den Brandt ◽  
W. Th. Wenckebach ◽  
J. Kohlbrecher ◽  
P. Hautle
Keyword(s):  
Neutron Scattering ◽  
Dynamic Nuclear Polarization ◽  
Small Angle ◽  
Nuclear Polarization ◽  
Spherical Particles ◽  
Neutron Spin ◽  
Triplet States ◽  
Spin Filter ◽  
Angle Scattering ◽  
Close Distance

A novel neutron spin filter whose principle is based on the strong spin dependence of the neutron scattering on protons has been developed. The dimensions of this filter are small, and it works very efficiently and is stable even in inhomogeneous fields. The protons in the naphthalene spin filter crystal are polarized by a recently developed method of dynamic nuclear polarization using photoexcited triplet states. This technique allows the design of a very compact apparatus that can be placed at a close distance to the sample under investigation. The application of this filter as a polarization analyzer is demonstrated in a magnetic small-angle neutron scattering experiment with the measurement of the spin-dependent scattering signals of a CuFeNi alloy. This sample has a pronounced textured structure factor of ferromagnetic precipitates in a paramagnetic matrix. The performance of the spin filter as an analyzer is illustrated by the excellent agreement of the experimental data with simulations based on a model of homogeneously magnetized spherical particles which are ordered in a simple cubic paracrystalline lattice.

scholarly journals Cryoprotectant-free high-pressure cooling and dynamic nuclear polarization for more sensitive detection of hydrogen in neutron protein crystallography

2018 ◽  
Vol 74 (8) ◽  
pp. 787-791 ◽  
Author(s):  
Ichiro Tanaka ◽  
Naoya Komatsuzaki ◽  
Wen-Xue Yue ◽  
Toshiyuki Chatake ◽  
Katsuhiro Kusaka ◽  
...  
Keyword(s):  
High Pressure ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Protein Crystals ◽  
Large Protein ◽  
Proton Polarization ◽  
Cooling Method ◽  
Small Crystals ◽  
Polarization Technique ◽  
Neutron Protein Crystallography

To improve the sensitivity of hydrogen detection using neutrons, a proton-polarization technique together with a high-pressure cooling method is necessary. The highest pressure (200 MPa) used in the experiment described here enabled relatively large protein crystals to be cooled without any cryoprotectants while retaining the protein structure, and it was confirmed that high-pressure-cooled crystals diffracted to nearly the same resolution as flash-cooled small crystals soaked with cryoprotectants. Dynamic nuclear polarization was used as a proton-polarization technique for protein crystals, and ∼300 mg polycrystalline protein doped with TEMPOL gave a maximum proton polarization of 22.3% at a temperature of 0.5 K in a 2.5 T magnetic field.

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