Radio-Frequency Manipulation of State Populations in an Entangled Fluorine-Muon-Fluorine System.

Entangled spin states are created by implanting muons into single-crystal LiY_{0.95}Ho_{0.05}F_{4} to form a cluster of correlated, dipole-coupled local magnetic moments.

Muon-Nitrogen Quadrupolar Level Crossing Resonance in a Charge Transfer Salt.

Although muons are primarily regarded as a local spin probe, they can also access the charge state of an atom or molecule via quadrupolar level crossing resonance (QLCR) spectroscopy. We use LiTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane), a simple charge transfer salt, to test the potential of this technique in molecular systems by studying the interaction of a positive muon with the TCNQ nitrogen atoms. We show that both a positive muon and muonium are able to add to the nitrogen, leading to a singlet spin state for the addition molecule.

Na-ion mobility in P2-type NaMgNiMnO (0 ≤ ≤ 0.07) from electrochemical and muon spin relaxation studies.

Sodium transition metal oxides with a layered structure are one of the most widely studied cathode materials for Na-ion batteries. Since the mobility of Na in such cathode materials is a key factor that governs the performance of material, electrochemical and muon spin rotation and relaxation techniques are here used to reveal the Na-ion mobility in a P2-type NaMgNiMnO ( = 0, 0.02, 0.

Complex magnetic properties associated with competing local and itinerant magnetism in [Formula: see text].

Ternary intermetallic compound [Formula: see text] has been synthesized in single phase and characterized by x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) analysis, magnetization, heat capacity, neutron diffraction and muon spin rotation/relaxation ([Formula: see text]SR) measurements. The polycrystalline compound was synthesized in single phase by introducing necessary vacancies in Co/Si sites. Magnetic, heat capacity, and zero-field neutron diffraction studies reveal that the system undergoes magnetic transition below [Formula: see text]4 K.

Dynamics of polystyrene probed by muon spin spectroscopy.

Muon spin spectroscopic measurements were made on atactic low-molecular-weight (LMW) (1.3 kg mol) and high-molecular-weight (HMW) (202 kg mol) polystyrene. Muoniated cyclohexadienyl radicals, which are formed by muonium addition to the phenyl side groups, are used as local probes of bulk dynamics.

Quantum spin-liquid states in an organic magnetic layer and molecular rotor hybrid.

The exotic properties of quantum spin liquids (QSLs) have continually been of interest since Anderson's 1973 ground-breaking idea. Geometrical frustration, quantum fluctuations, and low dimensionality are the most often evoked material's characteristics that favor the long-range fluctuating spin state without freezing into an ordered magnet or a spin glass at low temperatures. Among the few known QSL candidates, organic crystals have the advantage of having rich chemistry capable of finely tuning their microscopic parameters.

Magnetism and ion diffusion in honeycomb layered oxide [Formula: see text].

In the quest for developing novel and efficient batteries, a great interest has been raised for sustainable K-based honeycomb layer oxide materials, both for their application in energy devices as well as for their fundamental material properties. A key issue in the realization of efficient batteries based on such compounds, is to understand the K-ion diffusion mechanism. However, investigation of potassium-ion (K[Formula: see text]) dynamics in materials using e.

Rate constants and kinetic isotope effects for H-atom abstraction reactions by muonium in the Mu + propane and Mu + n-butane reactions from 300 K to 435 K: challenges for theory.

This paper reports measurements of the temperature dependence of the rate constants for H-atom abstraction reactions from propane and n-butane by the light isotopic H-atom muonium (Mu), k(T), over temperatures in the range 300 K to 435 K. Simple Arrhenius fits to these data yield activation energies, E, that are some 2-4 times lower than E found from corresponding fits for the H + propane and H + n-butane reactions studied elsewhere, both experimentally and theoretically, and fit over a similar temperature range. These activation energies E are also much lower than estimated from zero-point-energy corrected vibrationally adiabatic potential barriers, both results suggesting that quantum tunneling plays an important role in determining k(T) and for the Mu + propane reaction in particular.

Microscopic muon dynamics in the polymer electrolyte poly(ethylene oxide).

The microscopic dynamics of protons (H^{+}) in poly(ethylene oxide) (PEO) have been investigated through a study of implanted positive muons (Mu^{+}), which can be considered a light proton analog. The exponential decay of the muon spin polarization in zero magnetic field indicated that Mu^{+} hopping is in the fast fluctuation limit between 140 and 310 K and the relaxation rate was found to be sensitive to the glass transition. Mu^{+} dynamics in PEO was monitored via the relaxation of the muon spin polarization in a transverse field of 10 mT.

Discovery of slow magnetic fluctuations and critical slowing down in the pseudogap phase of YBaCuO .

The origin of the pseudogap region below a temperature * is at the heart of the mysteries of cuprate high-temperature superconductors. Unusual properties of the pseudogap phase, such as broken time-reversal and inversion symmetry are observed in several symmetry-sensitive experiments: polarized neutron diffraction, optical birefringence, dichroic angle-resolved photoemission spectroscopy, second harmonic generation, and polar Kerr effect. These properties suggest that the pseudogap region is a genuine thermodynamic phase and are predicted by theories invoking ordered loop currents or other forms of intra-unit-cell (IUC) magnetic order.

Li-ion diffusion in Li intercalated graphite CLi and CLi probed by μSR.

In order to study a diffusive behavior of Li in Li intercalated graphites, we have measured muon spin relaxation (μSR) spectra for CLi and CLi synthesized with an electrochemical reaction between Li and graphite in a Li-ion battery. For both compounds, it was found that Li ions start to diffuse above 230 K and the diffusive behavior obeys a thermal activation process. The activation energy (E) for CLi is obtained as 270(5) meV, while E = 170(20) meV for CLi.

Magnetic ordering of defects in a molecular spin-Peierls system.

With interest in charge transfer compounds growing steadily, it is important to understand all aspects of the underlying physics of these systems, including the properties of the defects and interfaces that are universally present in actual experimental systems. For the study of these defects and their interactions a spin-Peierls (SP) system provides a useful testing ground. This work presents an investigation within the SP phase of potassium TCNQF where anomalous features are observed in both the magnetic susceptibility and ESR spectra for temperatures between 60 K and 100 K.

Muonium Chemistry at Diiron Subsite Analogues of [FeFe]-Hydrogenase.

The chemistry of metal hydrides is implicated in a range of catalytic processes at metal centers. Gaining insight into the formation of such sites by protonation and/or electronation is therefore of significant value in fully exploiting the potential of such systems. Here, we show that the muonium radical (Mu ), used as a low isotopic mass analogue of hydrogen, can be exploited to probe the early stages of hydride formation at metal centers.

Questioning Antiferromagnetic Ordering in the Expanded Metal, Li(NH3)4: A Lack of Evidence from μSR.

We present the results of a muon spin relaxation study of the solid phases of the expanded metal, Li(NH3)4. No discernible change in muon depolarization dynamics is witnessed in the lowest temperature phase (≤25 K) of Li(NH3)4, thus suggesting that the prevailing view of antiferromagnetic ordering is incorrect. This is consistent with the most recent neutron diffraction data.

Rate constants for the slow Mu + propane abstraction reaction at 300 K by diamagnetic RF resonance.

The study of kinetic isotope effects for H-atom abstraction rates by incident H-atoms from the homologous series of lower mass alkanes (CH4, C2H6 and, here, C3H8) provides important tests of reaction rate theory on polyatomic systems. With a mass of only 0.114 amu, the most sensitive test is provided by the rates of the Mu atom.

The NeXus data format.

NeXus is an effort by an international group of scientists to define a common data exchange and archival format for neutron, X-ray and muon experiments. NeXus is built on top of the scientific data format HDF5 and adds domain-specific rules for organizing data within HDF5 files, in addition to a dictionary of well defined domain-specific field names. The NeXus data format has two purposes.

Hyperfine coupling constants of the cyclohexadienyl radical in benzene and dilute aqueous solution.

The muon hyperfine coupling constant (Aμ) of the muoniated cyclohexadienyl radical (C6H6Mu) has been directly measured in a 5 mM solution of benzene in water by the radio-frequency muon spin resonance (RF-μSR) technique. The relative shift of Aμ in aqueous solution compared with the value in neat benzene (ΔAμ/Aμ = +0.98(5)% at 293 K) can now be compared directly with theoretical predictions.

New results for the formation of a muoniated radical in the Mu + Br2 system: a van der Waals complex or evidence for vibrational bonding in Br-Mu-Br?

New evidence is presented for the observation of a muoniated radical in the Mu + Br(2) system, from μSR longitudinal field (LF) repolarisation studies in the gas phase, at Br(2) concentrations of 0.1 bar in a Br(2)/N(2) mixture at 300 K and at 10 bar total pressure. The LF repolarisation curve, up to a field of 4.

Spin evolution in a radio frequency field studied through muon spin resonance.

The application of composite inversion pulses to a novel area of magnetic resonance, namely muon spin resonance, is demonstrated. Results confirm that efficient spin inversion can readily be achieved using this technique, despite the challenging experimental setup required for beamline measurements and the short lifetime (≈2.2μs) associated with the positive muon probe.

Local magnetism in palladium bionanomaterials probed by muon spectroscopy.

Palladium bionanomaterial was manufactured using the sulfate-reducing bacterium, Desulfovibrio desulfuricansm, to reduce soluble Pd(II) ions to cell-bound Pd(0) in the presence of hydrogen. The biomaterial was examined using a Superconducting Quantum Interference Device (SQUID) to measure bulk magnetisation and by Muon Spin Rotation Spectroscopy (µSR) which is uniquely able to probe the local magnetic environment inside the sample. Results showed behaviour attributable to interaction of muons both with palladium electrons and the nuclei of hydrogen trapped in the particles during manufacture.

Conversion of cyclosporine to tacrolimus in stable renal allograft recipients: quantification of effects on the severity of gingival enlargement and hirsutism and patient-reported outcomes.

Background: Cyclosporine-induced side-effects such as gum enlargement and hirsutism potentially limit its effectiveness as a calcineurin-antagonist if these effects contribute to a lack of compliance. Although the differences in incidence of these effects are widely recognized, few studies are available to show the extent of reduced gum enlargement and hirsutism in patients converted from cyclosporine to tacrolimus. This study aimed to determine the efficacy and safety and patient-reported outcomes of such conversions.

Laser-muon spin spectroscopy in liquids - a technique to study the excited state chemistry of transients.

This study introduces laser-muon spin spectroscopy in the liquid phase, which extends muonium chemistry in liquids to the realm of excited states and enables the detection of muoniated molecules by their spin evolution after laser excitation. This leads to new opportunities to study the Kinetic Isotope Effects (KIEs) of muonium/atomic hydrogen reactions and to probe transient chemistry in radiolysis processes involved in muonium formation, as well as muoniated intermediates in excited states.

Muon implantation of metallocenes: ferrocene.

Muon Spin Relaxation and Avoided Level Crossing (ALC) measurements of ferrocene are reported. The main features observed are five high field resonances in the ALC spectrum at about 3.26, 2.

Muon spin relaxation study of Zr(H2PO4)(PO4).2H2O.

Muon spin relaxation has been used to study the muon dynamics in the layered zirconium phosphate Zr(H(2)PO(4))(PO(4)).2H(2)O as a function of temperature. Radiofrequency decoupling was used to establish the origin of the local dipolar field as coupling with (1)H spins.