Depth-resolved characterization of Meissner screening breakdown in surface treated niobium.

We report direct measurements of the magnetic field screening at the limits of the Meissner phase for two superconducting niobium (Nb) samples. The samples are processed with two different surface treatments that have been developed for superconducting radio-frequency (SRF) cavity applications-a "baseline" treatment and an oxygen-doping ("O-doping") treatment. The measurements show: (1) that the screening length is significantly longer in the "O-doping" sample compared to the "baseline" sample; (2) that the screening length near the limits of the Meissner phase increases with applied field; (3) the evolution of the screening profile as the material transitions from the Meissner phase to the mixed phase; and (4) a demonstration of the absence of any screening profile for the highest applied field, indicative of the full flux entering the sample.

A new high parallel-field spectrometer at TRIUMF's β-NMR facility.

A new high field spectrometer has been built to extend the capabilities of the β-detected nuclear magnetic resonance (β-NMR) facility at TRIUMF. This new beamline extension allows β-NMR spectroscopy to be performed with fields up to 200 mT parallel to a sample's surface (perpendicular to the ion beam), allowing depth-resolved studies of local electromagnetic fields with spin polarized probes at a much higher applied magnetic field than previously available in this configuration. The primary motivation and application is to allow studies of superconducting radio frequency (SRF) materials close to the critical fields of Nb metal, which is extensively used to fabricate SRF cavities.

Magnesium(II)-ATP Complexes in 1-Ethyl-3-Methylimidazolium Acetate Solutions Characterized by Mg β-Radiation-Detected NMR Spectroscopy.

The complexation of Mg with adenosine 5'-triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin- β-emitter Mg to study Mg -ATP complexation in 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) solutions using β-radiation-detected nuclear magnetic resonance (β-NMR). We demonstrate that (nuclear) spin-polarized Mg, following ion-implantation from an accelerator beamline into EMIM-Ac, binds to ATP within its radioactive lifetime before depolarizing.

Investigation of ionic and anomalous magnetic behavior in CrSe using Li β-NMR.

We have studied a mosaic of 1T-CrSe single crystals using β-detected nuclear magnetic resonance of Li from 4 to 300 K. We identify two broad resonances that show no evidence of quadrupolar splitting, indicating two magnetically distinct environments for the implanted ion. We observe stretched exponential spin lattice relaxation and a corresponding rate (1/ ) that increases monotonically above 200 K, consistent with the onset of ionic diffusion.

Direct observation of Mg complexes in ionic liquid solutions by Mg β-NMR spectroscopy.

NMR spectra of Mg2+ ions in ionic liquids were recorded using a highly sensitive variant of NMR spectroscopy known as β-NMR. The β-NMR spectra of MgCl2 in EMIM-Ac and EMIM-DCA compare favourably with conventional NMR, and exhibit linewidths of ∼3 ppm, allowing for discrimination of species with oxygen and nitrogen coordination.

Direct measurements of the temperature, depth and processing dependence of phenyl ring dynamics in polystyrene thin films by β-detected NMR.

There is indirect evidence that the dynamics of a polymer near a free surface are enhanced compared with the bulk but there are few studies of how dynamics varies with depth. β-Detected nuclear spin relaxation of implanted 8Li+ has been used to directly probe the temperature and depth dependence of the γ-relaxation mode, which is due to phenyl rings undergoing restricted rotation, in thin films of atactic deuterated polystyrene (PS-d8) and determine how the depth dependence of dynamics is affected by sample processing, such as annealing, floating on water and the inclusion of a surfactant, and by the presence of a buried interface. The activation energy for the γ-relaxation process is lower near the free surface.

β-NMR measurements of molecular-scale lithium-ion dynamics in poly(ethylene oxide)-lithium-salt thin films.

β-detected NMR (β-NMR) has been used to study the molecular-scale dynamics of lithium ions in thin films of poly(ethylene oxide) (PEO) containing either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium trifluoroacetate (LiTFA) salts at monomer-to-salt ratios (EO/Li) of 8.3. The results are compared with previous β-NMR measurements on pure PEO and PEO with lithium triflate (LiOTf) at the same loading [McKenzie et al.

Enhanced high-frequency molecular dynamics in the near-surface region of polystyrene thin films observed with β-NMR.

β-detected nuclear spin relaxation of (8)Li(+) has been used to probe the depth dependence of molecular dynamics in high- and low-molecular-weight deuterated polystyrene. The average nuclear spin-lattice relaxation rate, 1/T(avg)(1), is a measure of the spectral density of the polymer motion at the Larmor frequency (41 MHz at 6.55 T).

β-NMR measurements of lithium ion transport in thin films of pure and lithium-salt-doped poly(ethylene oxide).

β-Detected nuclear spin relaxation of (8)Li(+) has been used to study the microscopic diffusion of lithium ions in thin films of poly(ethylene oxide) (PEO), where the implanted lithium ions are present in extremely low concentration, and PEO with 30 wt % LiCF3SO3 over a wide range of temperatures both above and below the glass transition temperature. Recent measurements by Do et al. [Phys.