Proton Polarization Research Articles

New spin structure constraints on hyperfine splitting and proton Zemach radius

The 1S hyperfine splitting in hydrogen is measured to an impressive ppt precision and will soon be measured to ppm precision in muonic hydrogen. The latter measurement will rely on theoretical predictions, which are limited by knowledge of the proton polarizability effect Δpol. Data-driven evaluations of Δpol have long been in significant tension with baryon chiral perturbation theory. Here we present improved results for Δpol driven by new spin structure data, reducing the long-standing tension between theory and experiment and halving the dominating uncertainty in hyperfine splitting calculations.

Magnetic polarizability of octet baryons via lattice QCD

Drawing on recent advances in lattice QCD background-field techniques, the magnetic polarizability of octet baryons is calculated from the first principles of QCD. The results are presented in the context of new constituent quark model calculations providing a framework for understanding the lattice results and a direct comparison with simulation results at unphysical quark masses. Using smeared quark sources, low-lying Laplacian eigenmode projection and final-state Landau-mode projection, considerable attention is devoted to ensuring single-state isolation in the lattice correlation functions. We also introduce new weighting methods to reduce the sensitivity to correlation-function fits, averaging over many fits based on merit drawn from the full correlated χ2 of the fits. The techniques are implemented on the 323×64, 2+1-flavor dynamical-fermion lattices provided by the PACS-CS Collaboration following the introduction of uniform magnetic fields quantized to the lowest nontrivial values available. After some scaling of the constituent quark model parameters, we find the model captures the patterns observed in the lattice QCD results very well, providing important insights into the physics underpinning the magnetic polarizabilities. Finally, comparison with the most recent results from experiment proceeds through an effective field theory formalism which incorporates estimates of finite-volume corrections and small electroquenching corrections as the results are brought to the physical point. We find excellent agreement with experiment where available, including the proton and neutron polarizabilities. Published by the American Physical Society 2024

Large-enhancement nanoscale dynamic nuclear polarization near a silicon nanowire surface.

Dynamic nuclear polarization (DNP) has revolutionized the field of nuclear magnetic resonance spectroscopy, expanding its reach and capabilities to investigate diverse materials, biomolecules, and complex dynamic processes. Bringing high-efficiency DNP to the nanometer scale would open exciting avenues for studying nanoscale nuclear spin ensembles, such as single biomolecules, virus particles, and condensed matter systems. Combining pulsed DNP with nanoscale force-detected magnetic resonance measurements, we demonstrated a 100-fold enhancement in the Boltzmann polarization of proton spins in nanoscale sugar droplets at 6 kelvin and 0.33 tesla. Crucially, this enhancement corresponds to a factor of 200 reduction in the averaging time compared to measurements that rely on the detection of statistical fluctuations in nanoscale nuclear spin ensembles. These results substantially advance the capabilities of force-detected magnetic resonance detection as a practical tool for nanoscale imaging.

Creating high, portable proton polarization with photo-excited triplet DNP

Dynamic nuclear polarization (DNP) is a powerful tool to polarize nuclear spins and enhance the intensity of their magnetic resonance signal. For DNP a sample is doped with an agent providing unpaired electron spins. Then the sample is cooled in a strong magnetic field to polarize these electron spins and a microwave field is applied to transfer this polarization to the nuclear spins. While DNP is very efficient, it has two inherent issues: the electron spins needed to polarize the nuclear spins are also the main source of polarization decay. Furthermore, polarizing the electron spins requires strong magnets and powerful cryogenics, that may obstruct further use of the polarized nuclear spins.These issues can be addressed by using the electron spin of photo-excited triplet states for DNP. After DNP the light creating the electron spins can be shut off, thus eliminating the main source of decay of the nuclear polarization. Moreover, for some well-chosen molecules the photo-excitation process creates the triplet state in a highly polarized state, so magnets and cryogenics can be significantly simplified.The present article presents the state of the art of producing a high proton polarization – up to 0.80 – with a long lifetime – typically 50 h at liquid nitrogen temperature and in a field of 0.75 T – using the photo-excited triplet state of pentacene in a naphthalene host. It describes sample preparation, experimental equipment and procedures required to obtain this result, as well the theoretical background required to maximize the polarization transfer from the triplet spins to the proton spins and to optimize the photo-excitation process. It finishes with methods for long-distance transport and final application of polarized samples.

Conserving Polarization of Protons in the Nuclotron/JINR up to 3.5 GeV/c Using Correction Dipoles and a Weak Solenoid

Conserving Polarization of Protons in the Nuclotron/JINR up to 3.5 GeV/c Using Correction Dipoles and a Weak Solenoid

Studying the Possibility of Dynamic Spin Handling for Polarized Protons and Deuterons at the NICA Accelerator Complex

Studying the Possibility of Dynamic Spin Handling for Polarized Protons and Deuterons at the NICA Accelerator Complex

High-energy density cellulose nanofibre supercapacitors enabled by pseudo-solid water molecules

Compared with conventional electrochemical supercapacitors and lithium-ion batteries, the novel amorphous cellulose nanofibre (ACF) supercapacitor demonstrates superior electric storage capacity with a high-power density, owing to its fast-charging capability and high-voltage performance. This study unveils introduces an ACF supercapacitor characterised by a substantial energy density. This is achieved by integrating a singular layer of pseudo-solid water molecules (electrical resistivity of 1.11 × 108 Ω cm) with cellulose nanofibers (CNFs), establishing forming an electric double layer at the electrode interface. The enhanced energy storage in these high-energy density capacitors (8.55 J/m2) is explicated through the polarisation of protons and lone pair electrons on oxygen atoms during water electrolysis, commencing at 1.23 V. Improvements in energy density are attainable through CNF density enhancements and charging-current optimisation. The proposed ACF supercapacitor offers substantial promise for integration into the power sources of flexible and renewable paper-based electronic devices.

Exploring Dielectric and Magnetic Properties of Ni and Co Ferrites through Biopolymer Composite Films

This study explores the synthesis and characterization of chitosan/gelatine films incorporating nickel ferrite (NiFe2O4) and cobalt ferrite (CoFe2O4) nanoparticles. The magnetic nanoparticles exhibit superparamagnetic behaviour, making them attractive for various applications, including biomedical uses. The X-ray diffraction analysis confirmed the successful synthesis of NiFe2O4 and CoFe2O4 nanoparticles, and the scanning electron micrographs illustrated well-dispersed ferrite nanoparticles within the biopolymer network, despite the formation of some aggregates attributed to magnetic interactions. Magnetization loops revealed lower saturation magnetization values for the composites, attributed to the chitosan/gelatine coating and the dielectric studies, indicating increased dielectric losses in the presence of ferrites, particularly pronounced in the case of NiFe2O4, suggesting interactions at the interface region between the polymer and ferrite particles. The AC conductivity shows almost linear frequency dependence, associated with proton polarization and conduction processes, more significant at higher temperatures for samples with ferrite particles.

J/ψ and ψ(2S) polarization in proton-proton collisions at energies available at the CERN Large Hadron Collider using PYTHIA8

The production mechanisms of charmonium states in both hadronic and heavy-ion collisions hold great significance for investigating the hot and dense QCD matter. Studying charmonium polarization in ultrarelativistic collisions can also provide insights into the underlying production mechanisms. With this motivation, we explore the J/ψ and ψ(2S) polarization in proton+proton collisions at s=7, 8, and 13 TeV using a pQCD-inspired Monte Carlo event generator called 8. This work considers reconstructed quarkonia through their dimuons decay channel in the ALICE forward rapidity acceptance range of 2.5<yμμ<4. Further, we calculate the polarization parameters λθ, λϕ, λθϕ from the polar and azimuthal angular distributions of the dimuons in helicity and Collins-Soper frames. This study presents a comprehensive measurement of the polarization parameters as a function of transverse momentum, charged-particle multiplicity, and rapidity at the LHC energies. Our findings of charmonium polarization are in qualitative agreement with the corresponding experimental data. Published by the American Physical Society 2024

Recent Results on Proton Charge Radius and Polarizabilities

Recent Results on Proton Charge Radius and Polarizabilities

Combined performance of circularly polarized luminescence and proton conduction in homochiral cadmium(ii)–terbium(iii) complexes

A pair of Cd2Tb enantiomers shows coexsistence of CPL-active and proton conductive properties, offering a promising strategy for the development of multifunctional materials.

Commissioning results of the BNL Alternating Gradient Synchrotron booster AC dipole

An AC dipole has been installed in the AGS booster as part of polarized beam developments for the future Electron Ion Collider (EIC). This will allow preserving helion beam polarization through two intrinsic resonances during acceleration to an energy corresponding to |Gγ| = 10.5. AC dipoles can preserve polarization by forcing the beam to undergo large amplitude vertical betatron oscillations. These coherent oscillations cause all particles to sample the strong horizontal fields of quadrupoles, and result in a full spin flip. In preparation for the AC dipole being used for polarized helions, it was first commissioned with polarized protons. The proton extraction energy was raised to allow protons to cross Gγ=0+νy = 4.8087. As an artifact of the experiment using polarized protons, the booster settings for bunch extraction interfered with the coherent oscillations and limited the maximum coherent amplitude. This interference will be well separated in the case of polarized helions. Polarized protons crossed the Gγ=0+νy intrinsic resonance with a full spin flip through use of the AC dipole. Simulations of the resonance crossing using Zgoubi accurately predict the polarization relative to the coherent amplitude.

Theoretical and computational study of benzenium and toluenium isomers.

Four methods of computational quantum chemistry are used in a study of hyperconjugation in protonated aromatic molecules. Benzene, benzenium, toluene, and four isomeric forms of toluenium are examined using the self-consistent field level of theory followed by configuration interaction and coupled cluster calculations, as well as density functional theory. Results for proton affinities, geometric parameters, atomic populations, dipole moments, and polarizabilities are reported. The calculated results are in good agreement with previous computational studies and with experimental data. The presence of hyperconjugation is evident from the shortened carbon-carbon bond lengths in the aromatic ring and concomitant changes in dipole moments and polarizabilities. The proton affinities of benzene and toluene compare well with experimental values. The examination of all of the toluenium isomers reveals that the position of the methyl group has a minor impact on the strength of hyperconjugation, although the most stable isomer is found to be the para form. Mulliken population analyses indicate that the addition of a proton contributes to aromatic hyperconjugation and increases the strength of π-bonds at the expense of σ-bonds.

Efficient polarization redistribution in hyperpolarized 1-D-propane produced via pairwise parahydrogen addition

Parahydrogen-Induced Polarization (PHIP) is NMR hyperpolarization technique that has matured from fundamental science to a biomedical tool for production of hyperpolarized MRI contrast agents. The spin order of nascent parahydrogen-derived protons can be employed directly for enhancement of their NMR signals or for polarization transfer to other nuclei in the hydrogenation product. In this work, we study the process of pairwise parahydrogen addition to propylene, which results in symmetric propane molecule with substantially enhanced methyl and methylene NMR signals. Specifically, we have synthesized site-selectively isotopically labeled 3-d-propylene molecule to study polarization dynamics in the resulting monodeuterated propane after pairwise parahydrogen addition. The deuterium presence in the hyperpolarized propane product results in a minute isotope chemical shift effect allowing to distinguish the proton resonances of CH3 and CH2D groups at 600 MHz. Pairwise parahydrogen 1,2-addition to 3-d-propylene was first confirmed by performing the reaction inside a 600 MHz NMR spectrometer, i.e., in the weakly-coupled regime at 14 T, where proton polarization dynamics is restricted to the molecular sites of parahydrogen addition. However, when the pairwise parahydrogen addition is performed in the strongly-coupled regime, i.e., at the Earth's magnetic field, efficient polarization transfer to CH2D protons is readily observed, leading to polarization redistribution between the three inequivalent sites. This finding is important as it sheds light on polarization dynamics in the strongly coupled symmetric spin systems such as propane studied here—the presented results are expected to be applicable to other spin systems such as butane.

Chiral perturbation theory of the hyperfine splitting in (muonic) hydrogen

The ongoing experimental efforts to measure the hyperfine transition in muonic hydrogen prompt an accurate evaluation of the proton-structure effects. At the leading order in alpha , which is O(alpha ^5) in the hyperfine splitting (hfs), these effects are usually evaluated in a data-driven fashion, using the empirical information on the proton electromagnetic form factors and spin structure functions. Here we perform a first calculation based on the baryon chiral perturbation theory (Bchi PT). At leading orders it provides a prediction for the proton polarizability effects in hydrogen (H) and muonic hydrogen (mu H). We find large cancellations among the various contributions leading to, within the uncertainties, a zero polarizability effect at leading order in the Bchi PT expansion. This result is in significant disagreement with the current data-driven evaluations. The small polarizability effect implies a smaller Zemach radius R_textrm{Z}, if one uses the well-known experimental 1S hfs in H or the 2S hfs in mu H. We, respectively, obtain R_textrm{Z}(textrm{H}) = 1.010(9) fm, R_textrm{Z}(mu textrm{H}) = 1.040(33) fm. The total proton-structure effect to the hfs at O(alpha ^5) is then consistent with previous evaluations; the discrepancy in the polarizability is compensated by the smaller Zemach radius. Our recommended value for the 1S hfs in mu text {H} is 182.640(18),textrm{meV}.

Polarized Neutrons Observed Nanometer-Thick Crystalline Ice Plates in Frozen Glucose Solution.

Spin-contrast-variation (SCV) small-angle neutron scattering (SANS) is a technique to determine the nanostructure of composite materials from the scattering of polarized neutrons that changes with proton polarization of samples. The SCV-SANS enabled us to determine structure of nanoice crystals that were generated in rapidly frozen sugar solutions by separating the overlapped signals from the nanoice crystals and frozen amorphous solutions. In the frozen glucose solution, we found that the nanoice crystals formed a planar structure with a radius larger than several tens of nanometers and a thickness of 2.5 ± 0.5 nm, which was close to the critical nucleation size of ice crystals in supercooled water. This result suggests that the glucose molecules were preferentially bound to a specific face of nanoice crystals and then blocked the crystal growth perpendicular to that face.

Water distribution in human hair microstructure elucidated by spin contrast variation small-angle neutron scattering

Dynamic nuclear polarization (DNP) is effective for controlling the neutron scattering length of protons and can be utilized for contrast variation in small-angle neutron scattering (SANS). Using the TEMPOL solution soaking method as electron spin doping, the DNP–SANS technique was applied to human hair fiber for the first time. For dry and D2O-swollen hair samples, a drastic change in the SANS profile was observed at high polarization conditions (|P H P N| ∼ 60%, where P H and P N are the proton and neutron spin polarization, respectively). The SANS profile as a function of the magnitude of the scattering vector, q, was composed of a low-q upturn, a middle-q oscillation and a high-q flat region. The low-q upturn was assumed to be a combination of two power-law functions, q −4 due to a large structure interface (Porod's law) and q −2 due to random coil. The middle-q oscillation was well reproduced by numerical calculation based on the structure model of intermediate filaments (IFs) as proposed by Er Rafik et al. [Biophys. J. (2004), 86, 3893–3904]: one pair of keratin coiled-coils is located at the center and surrounded by seven pairs of keratin coiled-coils located in a circle (called the `7 + 1' model), and a collection of IFs is arranged in a quasi-hexagonal manner. For the observed SANS profiles for different P H P N, the IF term contribution maintained a constant q-dependent profile, despite significant changes in intensity. This indicates that the macrofibril is composed of two domains (keratin coiled-coils and matrix). In addition, D2O swelling enhanced the IF term intensity and shifted the polarization-dependent local minimum to higher P H P N. This behavior was reproduced by contrast factor calculation based on the two-domain model. Scattering length densities of keratin coiled-coil and surrounding matrix domains were calculated by use of the known amino acid composition, considering the hydrogen–deuterium exchange reaction during soaking with D2O solution of TEMPOL. As a result, it was found that for keratin coiled-coil domains, about 40% of the peptide backbone amide NH protons were replaced with deuterons. This means that 68% of the α-helix domain is rigid, but the rest is flexible to allow dynamic dissociation of the hydrogen bond. Furthermore, the local mass density of each domain was precisely evaluated. The obtained data are expected to be a guide for further detailed investigation of keratin and keratin-associated protein distribution. This approach is expected to be applied to a wide variety of bio-derived materials, which are water absorbing in general.

Nuclear-Electronic Orbital QM/MM Approach: Geometry Optimizations and Molecular Dynamics.

Hybrid quantum mechanical/molecular mechanical (QM/MM) methods allow simulations of chemical reactions in atomistic solvent and heterogeneous environments such as proteins. Herein, the nuclear-electronic orbital (NEO) QM/MM approach is introduced to enable the quantization of specified nuclei, typically protons, in the QM region using a method such as NEO-density functional theory (NEO-DFT). This approach includes proton delocalization, polarization, anharmonicity, and zero-point energy in geometry optimizations and dynamics. Expressions for the energies and analytical gradients associated with the NEO-QM/MM method, as well as the previously developed polarizable continuum model (NEO-PCM), are provided. Geometry optimizations of small organic molecules hydrogen bonded to water in either dielectric continuum solvent or explicit atomistic solvent illustrate that aqueous solvation can strengthen hydrogen-bonding interactions for the systems studied, as indicated by shorter intermolecular distances at the hydrogen-bond interface. We then performed a real-time direct dynamics simulation of a phenol molecule in explicit water using the NEO-QM/MM method. These developments and initial examples provide the foundation for future studies of nuclear-electronic quantum dynamics in complex chemical and biological environments.

Neutrino mean free path for proto–neutron star matter within the Skyrme model

The neutrino mean free path is evaluated in hot proto--neutron star matter under a strong magnetic field. We consider densities in the range $0.04\ensuremath{\le}\ensuremath{\rho}\ensuremath{\le}0.4\phantom{\rule{4pt}{0ex}}{\mathrm{fm}}^{\ensuremath{-}3}$, several proton fractions from symmetric matter up to pure neutron matter, temperatures up to 30 MeV, and two magnetic field strengths $B={10}^{17}$ and ${10}^{18}$ G. Polarized proto--neutron star matter is described within the nonrelativistic Hartree-Fock model using the LNS Skyrme interaction, where the proper treatment for instabilities for low densities and temperatures is implemented. Under the same conditions, the degree of polarization of protons is stronger than the one for neutrons. For the neutrino mean free path we consider three reactions: the neutrino-neutron and neutrino-proton scattering, $\ensuremath{\nu}+n\ensuremath{\rightarrow}{\ensuremath{\nu}}^{\ensuremath{'}}+{n}^{\ensuremath{'}}$ and $\ensuremath{\nu}+p\ensuremath{\rightarrow}{\ensuremath{\nu}}^{\ensuremath{'}}+{p}^{\ensuremath{'}}$, respectively, and the neutrino absorption reaction $\ensuremath{\nu}+n\ensuremath{\rightarrow}{e}^{\ensuremath{-}}+p$. The magnetic field induces an asymmetry in the mean free path which favors the flux of neutrinos parallel to the magnetic field in the case of neutron scattering and the absorption reaction, whereas it is antiparallel in the case of proton scattering. For most of the conditions the absorption reaction is the dominant one. The dependence of the neutrino mean free path on the magnetic field, the temperature, and the proton fraction is different for each reaction. As a representative case of our results, the asymmetry in the mean free path is $\ensuremath{\approx}21%$ at saturation density for $B={10}^{18}$ G, $T=15$ MeV, and symmetric matter, while we have $\ensuremath{\approx}\ensuremath{-}1%$ for $B={10}^{17}$ G and the same values of all the other conditions.

Polarised neutron scattering from dynamic polarised nuclei 1972–2022

With the inauguration of the small-angle instrument D11 of the Institute Laue–Langevin (ILL) in September 1972 neutron scattering revolutionized methods of contrast variation. Very soon D11 was oversubscribed by proposals relying on isotopic substitution of hydrogen isotopes. At the same time in Oxford first experiments of polarised neutron diffraction from dynamic polarised protons in lanthanum magnesium nitrate crystals demonstrated the great utility of this approach. In the early eighties a new type of polarised target material led to a boom of contrast variation by nuclear polarisation. The new samples of frozen solutions of macromolecules lent themselves to small-angle scattering. Often in collaboration with research centres of High Energy Physics various groups in Europe and Japan started experiments of polarized neutron scattering from dynamic polarised protons. Techniques of NMR and EPR considerably enlarged the spectrum of nuclear contrast variation. This is shown with time-resolved polarised neutron scattering from dynamic polarized proton spins of a free radical and of tyrosyl doped catalase using D22 at the ILL.Graphical abstract