Abstract We use implanted 8 Li + β -detected nuclear magnetic resonance ( β -NMR) measurements to “fingerprint” the Li + lattice sites in single crystals of rutile TiO 2 and MgF 2 via the quadrupolar splittings. Supplemented by density functional theory (DFT) calculations, we establish the equilibrium crystallographic Li + site, the Wyckoff 4 c site, and uncover a metastable Wyckoff 4 d site.

We investigate the behavior of interstitial Li + 8 implanted near the surface of 2 H − MoTe 2 using β -detected nuclear magnetic resonance. We find that, unlike the muon, Li + 8 does not show any signature of induced magnetism. This result is consistent with density functional theory, which identifies the Li stopping site at the 2a Wyckoff position in the van der Waals gap and confirms the absence of detectable Li-induced electronic spin polarization. Both the spin-lattice relaxation and the resonance line shape show evidence of pronounced spin dynamics above ∼ 200 K , reminiscent of local stochastic Li + 8 motion within a cage. The resonance line shape consists of quadrupolar satellites on top of a broad central peak. To better understand the interaction of Li + 8 with the host material, we employ a frequency-comb measurement by simultaneously exciting four frequencies corresponding to the first-order quadrupolar satellite transitions, ν 0 ± 3 ν comb and ν 0 ± ν comb , around the Larmor frequency ν 0 as a function of ν comb . This offers an enhanced sensitivity to the quadrupolar split portion of the line. Using this method, we find a small decrease in the quadrupolar frequency with increasing temperature, showing the typical behavior associated with thermally excited phonons and the absence of any magnetic response, in contrast to what was observed for other defects in 2 H − MoTe 2 .

We investigate the behavior of interstitial 8Li+ implanted near the surface of 2H-MoTe2 using beta-detected nuclear magnetic resonance. We find that, unlike the muon, 8Li+ does not show any signature of induced magnetism. This result is consistent with density functional theory, which identifies the Li stopping site at the 2a Wyckoff position in the van der Waals gap and confirms the absence of detectable Li-induced electronic spin polarization. Both the spin-lattice relaxation and the resonance line shape show evidence of pronounced spin dynamics above similar to 200 K, reminiscent of local stochastic 8Li+ motion within a cage. The resonance line shape consists of quadrupolar satellites on top of a broad central peak. To better understand the interaction of 8Li+ with the host material, we employ a frequency-comb measurement by simultaneously exciting four frequencies corresponding to the first-order quadrupolar satellite transitions, v0 +/- 3vcomb and v0 +/- vcomb, around the Larmor frequency v0 as a function of vcomb. This offers an enhanced sensitivity to the quadrupolar split portion of the line. Using this method, we find a small decrease in the quadrupolar frequency with increasing temperature, showing the typical behavior associated with thermally excited phonons and the absence of any magnetic response, in contrast to what was observed for other defects in 2H-MoTe2.

We report 9-detected nuclear magnetic resonance (9 NMR) measurements of implanted 8Li+ in a synthetic single crystal of alpha-SiO2 (quartz). At 6.55 Tesla, the spectrum is comprised of a large amplitude broad resonance and a quadrupolar multiplet that is only revealed by an rf comb excitation. The quadrupole splitting is surprisingly small, increases with temperature, and provides information on the implantation site. Supercell density functional theory calculations show the splitting is consistent with an in-channel interstitial site (Wyckoff 3a). The spinlattice relaxation is unexpectedly fast and strongly temperature dependent with a diffusive peak above 200 K and a second more prominent relaxation peak at lower temperature. Analysis of the diffusive relaxation yields an activation barrier 178(43) meV for the isolated Li+ in the range of other measurements and calculations. To account for many of the other features of the data, it is suggested that some of the implanted ions trap an electron forming the neutral Li0, which is stable over a narrow range of temperatures.

The TUCAN neutron electric dipole moment experiment utilizes the QuSpin Zero-Field Magnetometer (QZFM) to accurately map residual fields within a large magnetically shielded room. Three potential flaws of the QZFM are characterized in preparation for mapping. The magnetometer's intrinsic offset was measured to be within +/- 3 nT and stable over a period of one year. The response was shown to be within 2 percent of linearity in the zero-field regime, up to 2 nT(pp), and then follows a smooth dispersion curve. Crosstalk effects induced by multisensor operation were determined to have a small effect, and inconsequential with a separation above 6 cm. These results enable the QZFM for accurate measurement of DC fields, increase the operational range of QZFM by a factor of more than an order of magnitude, and allow for higher efficiency and flexibility by green-lighting simultaneous operation of multiple QZFMs.

The neutron electric dipole moment (EDM) is a sensitive probe for currently undiscovered sources of charge-parity symmetry violation. As part of the TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration, we are developing spin analyzers for ultracold neutrons (UCNs) to be used for a next-generation experiment to measure the neutron EDM with unprecedented precision. Spin-state analysis of UCNs constitutes an essential part of the neutron EDM measurement sequence. Magnetized iron films used as spin filters of UCNs are crucial experimental components, whose performance directly influences the statistical sensitivity of the measurement. To test such iron film spin filters, we propose the use of polarized cold-neutron reflectometry, in addition to conventional UCN transmission experiments. The new method provides information on iron film samples complementary to the UCN tests and accelerates the development cycles. We developed a collaborative effort to produce iron film spin filters and test them with cold and ultracold neutrons available at JRR-3/MINE2 and J-PARC/MLF BL05. In this article, we review the methods of neutron EDM measurements, discuss the complementarity of this new approach to test UCN spin filters, provide an overview of our related activities, and present the first results of polarized cold-neutron reflectometry recently conducted at the MINE2 beamline.

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. Measurements are performed utilizing the β -detected nuclear magnetic resonance ( β -NMR) technique that allows depth resolved studies of the local magnetic field within the first 100 nm of the surface. The study takes advantage of the β -SRF beamline, a new facility at TRIUMF, Canada, where field levels up to 200 mT are available parallel to the sample surface to replicate radio frequency fields near the Meissner breakdown limits of Nb.

The inverse perovskite Sr 3 SnO is a 3D cubic Dirac semimetal with a very small energy gap[1]. Its unusual electronic structure confers a variety of novel properties, such as chiral topological surface states, and very strong itinerant electron orbital magnetism. Remarkably, when doped it also becomes superconducting[2]. In the lowest carrier density samples, the Fermi level lies close to the Dirac points, and orbital magnetism is maximal. Here we report the results of ion-implanted 8 Li + β NMR in Au-capped epitaxial thin films of Sr 3 SnO as a function of carrier content. In addition, we stop the 8 Li in the Au overlayer to seek proximal evidence of the chiral surface state. In high magnetic field (6.55 T), we find remarkably little contrast in spin-lattice relaxation (SLR) between low carrier density Sr 3 SnO and the Au overlayer. In the inverse perovskite layer, 1/ T 1 ∼ 0.14 s -1 , slightly faster than Au at 300 K, while in the overlayer, there is a small but systematic enhancement in 1/ T 1 compared to a control film of Au. The resonance in the Sr 3 SnO layer is broad with a long tail towards negative shift without resolved quadrupolar splitting.

We present high (> 2 T) magnetic field β NMR measurements of 8 Li + implanted in single crystals of sapphire, a commonly used backing material for other samples. From the well-resolved quadrupolar splitting, we extract the electric field gradient (EFG) at the implanted 8 Li + site. Comparison with supercell density functional theory calculations of the EFG allows us to identify the octahedral interstitial site as the most likely candidate. In contrast to the zero field β NQR spectra, where multiple singals are detected, only a single site is evident at high field. We discuss possible explanations for this discrepancy. The spin lattice relaxation is extremely slow (1/ T 1 < 0.02 s −1 ) over a broad temperature range from 4 to 300 K, demonstrating that cross relaxation with the 27 Al nuclear spins is quenched in such high magnetic fields.

In our prior work, we showed that β -detected nuclear magnetic resonance ( β -NMR) was a good probe of bulk room temperature ionic liquid (RTIL) dynamics and dynamic heterogeneity. We now investigate how the surface modifies these properties, presenting the first depth-resolved β -NMR measurements in 1-ethyl-3-methylimidazolium acetate as a liquid, supercooled liquid, and glass. This interfacial region is important for understanding how constrained dimensionality affects dynamics. We show that both the surface and the glass transition have a large impact on molecular dynamics, which in many aspects differs greatly from our expectations based on polymer glasses. For example, in the glassy phase the surface dynamics appear to be faster than in the bulk (i.e., liquid-like), yet just as heterogeneous (i.e., glass-like).

The molecular dynamics of inelastic strain in glasses remains poorly understood, in contrast to the plasticity of crystalline materials that is well-characterized by measurements of dislocation activity. We report initial results on a 300 nm thick atactic polystyrene film undergoing plastic strain in its glassy state. This physical modification was applied by nanoimprint stamping with a 1 mm ultra-smooth spherical die to induce a stress exceeding mechanical yield (0.8% residual strain). Using 8 Li implanted-ion β NMR, we monitor the spin-lattice relaxation to infer depth-resolved rates of molecular dynamics. We find a significant change in the bulk molecular dynamics of the imprinted film (away from the surface) compared to an identically prepared control film. The relaxation is ∼ 20% slower in the film left densified by imprinting. We expect this relaxation to be coupled to the motion of the phenyl side rings; wherein slower dynamics due to densification is reasonable, as tighter packing should increase the energy barrier to molecular motion. In addition, we see an increase in the apparent thickness of a nanometric mobile surface layer, but this may be an artefact of surface roughening caused by imprinting.

We report the β -detected NMR of implanted 8 Li + in the rhombohedrally distorted perovskite LaAlO 3 . As observed in other insulating perovskites, the resonance has large quadrupolar splitting. However, it exhibits additional splitting due to the rhombohedral distortion. In addition, the magnitude of the electric field gradient at the 8 Li site is larger than in cubic perovskites, such as SrTiO 3 , with v Q ≈ 191.3 kHz.

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. The details of the design considerations and implementation of the ultra-high vacuum (UHV) system, ion optics, and beam diagnostics are presented here. Commissioning of the beamline and spectrometer with radioactive ions are also reported here. Future capabilities and applications in other areas are also described.

We report $\beta$-detected nuclear magnetic resonance of ultra-dilute $^{8}$Li$^{+}$ implanted in highly oriented pyrolytic graphite (HOPG). The absence of motional narrowing and diffusional spin-lattice relaxation implies Li$^+$ is not appreciably mobile up to 400 K, in sharp contrast to the highly lithiated stage compounds. However, the relaxation is remarkably fast and persists down to cryogenic temperatures. Ruling out extrinsic paramagnetic impurities and intrinsic ferromagnetism, we conclude the relaxation is due to paramagnetic centers correlated with implantation. While the resulting effects are not consistent with a Kondo impurity, they also differ from free paramagnetic centers, and we suggest that a resonant scattering approach may account for much of the observed phenomenology.

Spin lattice relaxation is the simplest type of β NMR measurement. The usual approach is to implant a pulse of hyperpolarized nuclei and monitor the time-resolved β-decay asymmetry, yielding the ensemble average spin-lattice relaxation. In the simplest case, the asymmetry decays exponentially with a characteristic time constant T 1 , but this ideal is rarely obtained in practice. In most data, the relaxation is more complicated. This can be the result of multiple crystallographic sites for the implanted probe each having a distinct T 1 . The sample may also be inhomogeneous due to: impurities or defects (including interfaces that are particularly important for thin films), intrinsic phase separation, or, if it is a glass. There may also be a background signal from probe ions that stop outside the sample. The general approach to this problem has been the ad hoc development of an appropriate relaxation model that avoids overparametrization. Given the prevalence of more complicated relaxation, it is crucial to develop a systematic approach to relaxation modelling. The decomposition of a relaxing signal into exponentials is, however, a mathematically ill-posed problem[1]. This feature is intrinsic and unavoidable, but there are a number of methods to accommodate it for noisy real-world data, including nuclear spin relaxation[2, 3, 4]. Here we demonstrate one of the best and most commonly used methods, Tikhonov regularization for the inverse Laplace transform, implemented for the particular features of β NMR relaxation data, most importantly the strong time dependence of the statistical uncertainty stemming from the radioactive lifetime of the probe.

Currently, no known material retains its photoinduced metallicconductivity over a long time while also exhibiting repeatable metal-to-insulatorrecovery. Here, we demonstrate such a highly repeatable photoinduced insulator-to-metal transition in yttrium oxyhydride (YOxHy) epitaxial thinfilms. The temperature(T) dependence of the electrical resistivity (rho) of thefilms transforms from theinsulating to the metallic state (d rho/dT> 0) under ultraviolet laser illumination. TheYOxHyfilm recovers its original insulating state when heated (125 degrees C) under an Aratmosphere and regains metallic conductivity when subsequently subjected toultraviolet laser illumination again, showing a repeatable photoinduced insulator-to-metal transition. First-principles calculations show that the itinerant carriers originate from the variations in the charge states of thehydrogen atoms that occupy octahedral interstitial sites. This study indicates that tuning the site occupancy (octahedral/tetrahedral)of the hydrogen atoms exerts a significant effect on the photoresponse of metal hydrides

The complexation of MgII with adenosine 5'-triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin- 1/2 β-emitter 31 Mg to study MgII -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 31 Mg, following ion-implantation from an accelerator beamline into EMIM-Ac, binds to ATP within its radioactive lifetime before depolarizing. The evolution of the spectra with solute concentration indicates that the implanted 31 Mg initially bind to the solvent acetate anions, whereafter they undergo dynamic exchange and form either a mono- (31 Mg-ATP) or di-nuclear (31 MgMg-ATP) complex. The chemical shift of 31 Mg-ATP is observed up-field of 31 MgMg-ATP, in accord with quantum chemical calculations. These observations constitute a crucial advance towards using β-NMR to probe chemistry and biochemistry in solution.

We report on the stability and magnetic state of ion implanted $^8$Li in single crystals of the semiconductor ZnO using $\beta$-detected nuclear magnetic resonance. At ultradilute concentrations, the spectra reveal distinct Li sites from 7.6 to 400 K. Ionized shallow donor interstitial Li is stable across the entire temperature range, confirming its ability to self-compensate the acceptor character of its (Zn) substitutional counterpart. Above 300 K, spin-lattice relaxation indicates the onset of correlated local motion of interacting defects, and the spectra show a site change transition from disordered configurations to substitutional. Like the interstitial, the substitutional shows no resolved hyperfine splitting, indicating it is also fully ionized above 210 K. The electric field gradient at the interstitial $^8$Li exhibits substantial temperature dependence with a power law typical of non-cubic metals.

The TRIUMF Ultra-Cold Advanced Neutron (TUCAN) collaboration aims at a precision neutron electric dipole moment (nEDM) measurement with an uncertainty of 10 − 27 e · cm, which is an order-of-magnitude better than the current nEDM upper limit and enables us to test Supersymmetry. To achieve this precision, we are developing a new high-intensity ultracold neutron (UCN) source using super-thermal UCN production in superfluid helium (He-II) and a nEDM spectrometer. The current development status of them is reported in this article.

Alginate and galactomannan-derived oligosaccharides enhanced the production of penicillin G when added to stirred tank reactor cultures of Penicillium chrysogenum. The addition of oligomannuronate and oligoguluronate blocks increased penicillin G yield by 47% and 49%, respectively. The effect of mannan oligosaccharides was found to be more pronounced with 69% higher yield than the control cultures. The maximum increase in the average specific productivity of the oligosaccharide augmented cultures was 55% after addition of mannan oligosaccharides. In addition, a difference was observed in all cases in the accumulation pattern of the intermediate of penicillin biosynthesis, delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine.