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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), kMu(T), over temperatures in the range 300 K to 435 K. Simple Arrhenius fits to these data yield activation energies, EMua, that are some 2–4 times lower than EHa 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 EMua 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 kMu(T) and for the Mu + propane reaction in particular. The results are expected to pose a considerable challenge to reaction rate theory for isotopic H-atom reactions in alkane systems.

We perform detailed muon spin rotation ($\ensuremath{\mu}\mathrm{SR}$) measurements in the classic antiferromagnet ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ and explain the spectra by considering dynamic population and dissociation of charge-neutral muon-polaron complexes. We show that charge-neutral muon states in ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$, despite lacking the signatures typical of charge-neutral muonium centers in nonmagnetic materials, have a significant impact on the measured $\ensuremath{\mu}\mathrm{SR}$ frequencies and relaxation rates. Our identification of such polaronic muon centers in ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ suggests that isolated hydrogen (H) impurities form analogous complexes, and that H interstitials may be a source of charge carrier density in ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$.

An $A$-type antiferromagnet, ${\mathrm{NaNiO}}_{2}$, was examined by means of positive muon spin rotation and relaxation (${\ensuremath{\mu}}^{+}\mathrm{SR}$) measurements and first-principles calculations based on a density functional theory (DFT). Below ${T}_{\mathrm{N}}=20$ K, a clear muon spin precession signal was observed in the ${\ensuremath{\mu}}^{+}\mathrm{SR}$ time spectrum recorded under zero field, due to the formation of a static internal magnetic field. The microscopic origin of such an internal field was computed as a sum of dipolar and hyperfine contact fields at the site (0.624, 0, 0.854), where both the muon site and the local spin density at such a site were predicted with DFT calculations. While the computed values were consistent with experimentally obtained ones, in both the antiferromagnetic and the paramagnetic states, the contribution of the hyperfine contact field was shown to be insignificant even below ${T}_{\mathrm{N}}$. Finally, measurements at higher temperatures signified thermally activated Na-ion diffusion with ${E}_{\mathrm{a}}=50(20)$ meV and ${D}_{\mathrm{Na}}(300\phantom{\rule{0.16em}{0ex}}\mathrm{K})=8.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}$/s, commonly observed in layered-type compounds.

We perform detailed muon spin rotation (μSR) measurements in the classic antiferromagnet Fe_{2}O_{3} and explain the spectra by considering dynamic population and dissociation of charge-neutral muon-polaron complexes. We show that charge-neutral muon states in Fe_{2}O_{3}, despite lacking the signatures typical of charge-neutral muonium centers in nonmagnetic materials, have a significant impact on the measured μSR frequencies and relaxation rates. Our identification of such polaronic muon centers in Fe_{2}O_{3} suggests that isolated hydrogen (H) impurities form analogous complexes, and that H interstitials may be a source of charge carrier density in Fe_{2}O_{3}.

Experiments reveal muon-polaron complexes in Cr${}_{2}$O${}_{3}$. Similar entities may exist in many magnetic insulators and semiconductors, where they can be used as proxies to understand the impact of hydrogen impurities.

Psychologists have a responsibility to be advocates for the individuals they serve within public service settings, and there is a need to identify or develop training strategies to support these efforts. Low-income families are a subset of consumers who frequently require services within these settings yet also may face providers who are not optimally supportive. One factor that interferes with providers' ability to engage in empathic, well-informed, and effective advocacy is their underlying attributions about causes of poverty that overemphasize personal responsibility. The current studies examined whether a poverty simulation training would be sufficient to modify participants' poverty attributions. Undergraduate participants in Study 1 (N = 126, Mean age = 21.6, SD = 5.6) were significantly more likely to emphasize external causes of poverty following the simulation. In Study 2, social service providers (N = 98, Mean age = 38.58, SD = 11.56) reported lower internal beliefs following participation in a poverty simulation but did not shift to a predominantly external belief index. The results of these studies demonstrate that causal attributions of poverty within both student and professional samples can be modified by participation in a poverty simulation. Because these attributions have important implications for advocacy work with consumers and efforts to address poverty, the poverty simulation experience has the potential to be an effective training tool that could yield real-world impact. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Gold nanoparticles (AuNPs) have been a subject of considerable interest in recent years due to both their magnetic and catalytic properties. This paper reports a two-fold study of the reactivity at...

The rate constant for the H atom abstraction reaction from methane by the muonic helium atom, Heμ + CH4 → HeμH + CH3, is reported at 500 K and compared with theory, providing an important test of both the potential energy surface (PES) and reaction rate theory for the prototypical polyatomic CH5 reaction system. The theory used to characterize this reaction includes both variational transition-state (CVT/μOMT) theory (VTST) and ring polymer molecular dynamics (RPMD) calculations on a recently developed PES, which are compared as well with earlier calculations on different PESs for the H, D, and Mu + CH4 reactions, the latter, in particular, providing for a variation in atomic mass by a factor of 36. Though rigorous quantum calculations have been carried out for the H + CH4 reaction, these have not yet been extended to the isotopologues of this reaction (in contrast to H3), so it is important to provide tests of less rigorous theories in comparison with kinetic isotope effects measured by experiment. In this regard, the agreement between the VTST and RPMD calculations and experiment for the rate constant of the Heμ + CH4 reaction at 500 K is excellent, within 10% in both cases, which overlaps with experimental error.

The local magnetic properties of Tm12Co 5Bi were investigated using muon spin relaxation (μSR), showing unusual magnetic features. Below 0.27 T, any magnetic transition in the sample occurs below ∼ 3 K while at 2.7 and 5 T, there is a magnetic transition in the range 10–30 K. These results constitute a possibility of a phase transition from an antiferromagnetic ground state to a short-ranged magnetic phase at the local level.

A first complete μSR study of the T dependences of the (reduced) muon, Aμ′(T), and proton, Ap(T), β-hyperfine coupling constants (hfcc) of the muoniated t-butyl radical is reported in the faujasitic zeolites NaY and USY, and the results are compared with similar data and with early EPR results in condensed bulk phases. The results are also compared with single-molecule UMP2 and DFT/B3LYP calculations in the bulk and in an NaY zeolite fragment of Si and O atoms with both OH- and H-capping. Muon hfcc are reported for the first time for the Mu-isobutyl radical in the bulk phase and are also compared with theory and with EPR data. The present results for the muon and proton hfcc of Mu-t-butyl in the bulk complement earlier work published elsewhere at higher temperatures but are extended here down to 5 K to facilitate comparisons with in vacuo theory at 0 K. Good fits to the data for both Aμ′(T) and Ap(T) for Mu-t-butyl are found from the calculated hfcc in both the bulk and in NaY, assuming a Boltzmann-weight...

We study the freezing of magnetic fluctuations in an Fe rich sample of the “11” iron-based superconductor using longitudinal field muon spin relaxation. The magnetic relaxation rate peaks at 15 K indicating spin glass freezing that nearly coincides with the superconducting transition of the corresponding Fe stoichiometric phase. At this temperature, the magnetic field dependence of the relaxation indicates slow magnetic fluctuations on the nanosecond timescale.

Temperature-dependent reaction rates have been measured for the reaction of muonic helium with ammonia 4.11 H + NH 3 ↔ 4.11 HH + NH 2 where 4.11 H representsthe muonicHeatom–Hewithone electron replacedbyanegative muon–whichbehaves chemicallyasaveryheavyisotopeofhydrogen,as emphasizedbythe (nonstandard)symbol. The Arrhenius activation energy was measured as 47 ± 17 kJ/mol between 400 and 600 K. The large uncertainty easily overlaps the value of 57 kJ/mol measured for the normalH + NH3 reaction [Ko et al., J. Phys. Chem. 94 (1990) 1401], and also existing calculations. The use of NH 3 as the electron donor in the production of neutral muonic He is discussed in light of the title reaction, and in comparison with alternatives Xe and CH 4 .

The interaction of muoniated cyclohexadienyl radicals with zeolite environments in NaY, HY, and USY has been studied using mainly avoided level crossing muon spin rotation (ALC-μSR) spectroscopy, w...

The intermetallic magnetic compound YbCrSb 3 , which shows anomalous behavior when compared to other compounds in the RECrSb 3 series, is studied near zero magnetic field using μ SR . Coherent muon spin precession is observed, unambiguously establishing at the local level that a significant fraction of the sample is in a well-ordered magnetic state below ≈ 240 K . These results confirm, at the local level, that the magnetic transition temperature in YbCrSb 3 is higher than those of the other RECrSb 3 compounds synthesized to date.

The muonic atom He 4 μ has the composition α ++ μ - e - , and is formed by stopping negative muons in He doped with a small amount of NH 3 (or Xe). It may be regarded as a unique heavy H-atom isotope with a mass of 4.1 amu. As such, the study of its chemical reaction rates and comparison with those of the well-known light Mu atom (0.113 amu) allows unprecedented tests of kinetic isotope effects over a range of 36 in mass. As a first example, and one which is of most fundamental interest, we have begun kinetics studies of the He μ + H 2 → He μ H + H reaction in the gas phase. The first measurements, at 295 K, give a rate constant of k He μ = 4.1 ± 0.7 × 10 - 16 cm 3 molec - 1 s - 1 . In comparison, variational transition state calculations give a value of 2.46 × 10 - 16 cm 3 molec - 1 s - 1 , somewhat below the measurement, despite the large error bar, raising the possibility that the calculations, on an essentially exact potential energy surface, have underestimated the amount of quantum tunneling involved, even for this heavy H-atom isotope.

The adsorption and dynamical behavior of the Mu−ethyl radical (MuC2H4) in NaY, HY, and USY faujasites was investigated by the muon spin resonance (μSR) technique, at loadings of one to five ethene molecules per supercage and over a temperature range of ca. 5−500 K (for NaY). The temperature dependences of both the muon and proton hyperfine coupling constants (Hfc's) are reported and compared with similar studies of MuC2H4 in different environments. Both transverse field (TF) μSR and avoided level crossing resonance (ALC) μSR spectra were recorded, with information on molecular motion mainly provided by the ALC line shapes. The muon Hfc's show only a small sensitivity to different frameworks and loadings but exhibit significant (∼10%) shifts at low temperatures, in comparison with bulk values, due to binding of the ethyl radical to cations at SII sites in NaY and to framework hydroxyls in the case of HY(USY). The Δ1 resonances are symmetric and quite broad at the lower temperatures studied, but dramaticall...

We report muon spin rotation studies on the magnetic properties of the newly discovered compound Ho12Co5Bi. We find that the material undergoes a bulk transition at TC ≈ 30 K to a magnetically ordered state. In the paramagnetic regime, we find slow magnetic fluctuations that persist far above TC. The fluctuations are found to be consistent with metallic spin fluctuations, but with a pronounced change of character at 110 K.

β -NMR of isolated 8Li has been investigated in the normal state of 2H- NbSe 2 . In a high magnetic field of 3 T a single resonance is observed with a Gaussian line width of 3.5 kHz. The line shape varies weakly as function of magnetic field and temperature but has a strong orientation dependence. The nuclear electric quadrupole splitting is unresolved implying that the electric field gradients are 10–100 times smaller than in other non-cubic crystals. The nuclear spin relaxation rate is also anomalously small but varies linearly with temperature as expected for Korringa relaxation in a metal. These results suggest that Li adopts an interstitial position between the weakly coupled NbSe 2 layers and away from the conduction band.

A spectrometer for β-detected nuclear magnetic resonance (β-NMR) has been commissioned at the ISAC facility at TRIUMF. A beam of low energy highly spin polarized 8Li+ can be decelerated and implanted into ultra-thin structures 6–400 nm thick. β-NMR provides local information on the electronic and magnetic properties of materials which is similar to conventional NMR but can be used as a sensitive probe of ultra-thin films, interfaces and other nanostructures. We report here on the status of the spectrometer and preliminary results on a simple metal film.

The precession signals of the muoniated ethyl radical have been studied as a function of ethene pressure in pure ethene, ethene/nitrogen mixtures and ethene/helium mixtures. The purpose was to investigate the kinetics and mechanism of the radical formation process. It is possible to fit the signal amplitudes with a model involving a single reaction step—Mu addition to ethene. However, the rate constant deduced from the model fit is significantly higher than the literature value for a thermal reaction, as determined by direct study of Mu decay in low partial pressures of ethene. The conclusion is that at partial pressures above 1 bar the reaction occurs before the incoming (beam) muons are fully thermalized.

We describe a new spectrometer and associated data-acquisition system, called MULTI, that is aimed at increasing the rate of data collection at continuous muon facilities by an order of magnitude.

Muonium has been directly detected over a range of temperatures and fields by transverse field μSR in different zeolites: 3A, 13X, USY, ZSM-5, and S-115 (a high-silica form of ZSM-5), as well as in silica gel. The polarizations determined from data at 75 and 150 G were independent of both field and temperature. The amounts of Mu seen vary from ∼20% to 40%, with a large missing fraction seen in every case, which may be partly due to slow Mu formation. There is also a fast Mu relaxation rate seen in all samples. This is the first direct observation of Mu in zeolites.

We have commissioned a polarized low-energy 8 Li ion beam line, which together with a high-field β-NMR spectrometer, can act as sensitive new probe of thin films and interfaces. The implantation energy can be continuously adjusted from 1 to 90 keV and the maximum polarization achieved thus far is 80%. This instrument opens up new applications for β-NMR which parallel and complement efforts with low-energy muons. For example, it is possible to probe the magnetic field distribution near the surface of a material by stopping a polarized 8 Li beam in a thin overlayer of Ag. Since the 8 Li adopts a site with cubic symmetry in Ag there is no quadrupolar splitting of the resonance, and the 8 Li acts as a purely magnetic sensor.

Muon spin rotation/relaxation measurements show clear evidence for magnetism in 2.2 nm gold nanoparticles capped with butanethiol. At low temperatures (1.8 K), there is significant spin relaxation which decreases as a function of both the applied longitudinal magnetic field and increasing temperature. The results indicate that there are spatially inhomogeneous electronic moments that fluctuate with a wide distribution of correlation times. Possible explanations are discussed.

The kinetics of the addition reaction of muonium (Mu) to acetylene have been studied in the gas phase at N2 moderator pressures mainly from ∼800 to 1000 Torr and over the temperature range from 168 to 446 K, but also down to 200 Torr at 168 K and over a much higher range of pressures, from 10 to 44 bar at 295 K, demonstrating pressure-independent rate constants, kMu(T). Even at 200 Torr moderator pressure, the kinetics for Mu + C2H2 addition behave as if effectively in the high-pressure limit, giving k∞ = kMu due to depolarization of the muon spin in the MuC2H2 radical formed in the addition step. The rate constants kMu(T) exhibit modest Arrhenius curvature over the range of measured temperatures. Comparisons with data and with calculations for the corresponding H(D) + C2H2 addition reactions reveal a much faster rate for the Mu reaction at the lowest temperatures, by 2 orders of magnitude, in accord with the propensity of Mu to undergo quantum tunneling. Moreover, isotopic atom exchange, which contributes in a major way to the analogous D atom reaction, forming C2HD + H, is expected to be unimportant in the case of Mu addition, a consequence of the much higher zero-point energy and hence weaker C-Mu bond that would form, meaning that the present report of the Mu + C2H2 reaction is effectively the only experimental study of kinetic isotope effects in the high-pressure limit for H-atom addition to acetylene.

The adsorption and dynamical behavior of the muonated cyclohexadienyl radical (C6H6Mu) in NaY zeolite, formed by muonium (Mu) addition on adsorbed benzene, was investigated by the muon spin resonance (μSR) technique, primarily at loadings of 2−3 C6H6 molecules per supercage of NaY. The dynamics of this radical are expected to be the same as its isotopic analogue, C6H7, for which there are no similar data available. Both TF-μSR and ALC-μSR spectra were recorded, with the most detailed information provided by the positions and line widths of the avoided level crossing resonances. In concert with 2H NMR, neutron diffraction and molecular dynamics studies of the parent benzene molecule, as well as current theoretical calculations, the dominant adsorption site for the C6H6Mu radical is believed to be the SII Na cation, within a supercage, which gives rise to three observed ALC lines, corresponding to two different orientations for the muon (proton) of the CHMu methylene group: pointing toward (endo) and away ...

Darbepoetin alfa is a novel erythropoiesis stimulating protein (NESP), which stimulates erythropoiesis by the same mechanism as recombinant human erythropoietin (rHuEPO). NESP has been shown to be safe and efficacious in patients with chronic renal failure. NESP is biochemically distinct from rHuEPO, due to its increased sialic acid content. NESP has an approximately 3-fold greater half-life. rHuEPO has been shown to be safe and effective for the treatment of chemotherapy-induced anaemia. This study assessed the safety and efficacy of NESP administered once per week, under the supervision of a physician, to patients with solid tumours who were receiving multicycle chemotherapy for up to 12 weeks. Three dose cohorts are presented in this sequential, unblinded and dose-escalating study. Thirteen to 59 patients received NESP (0.5, 1.5 or 2.25 mcg kg−1wk−1) in each cohort. Patients were monitored for adverse events, including antibody formation to NESP and for effects on haemoglobin. NESP appeared to be well tolerated. Adverse events were similar across all cohorts and were consistent with the population being studied. No antibody formation was detected over the 16-week study period and follow-up. A dose–response relationship was evident for NESP and multiple measures of efficacy, including proportion of patients responding to NESP and the mean change in haemoglobin by week 4 and end of treatment for NESP 0.5, 1.5 and 2.25 mcg kg−1wk−1cohorts (mean change in haemoglobin at end of treatment was 1.24, 1.73 and 2.15 g dl−1respectively). Controlled studies of this agent at higher doses and less frequent schedules of administration are ongoing. © 2001 Cance Cancer Research Campaign

The rate of the addition reaction H+O2→HO2 is measured at high O2 concentrations (up to 40 bar of O2 at room temperature) through its competition with rapid spin exchange, to give k ch 0 =8.7±0.8×10 −33 cm 6 s −1 .

The hyperfine interactions of the MuC6H6 radical in NaY zeolites at low to moderate benzene loadings have been measured by both the FT-μSR and ALC-μSR techniques over a wide temperature range. From a preliminary interpretation of the data, the hyperfine coupling constants for the muon and proton of the – CHMu methylene group in two different orientations for the radical bound to the SII cation site have been determined. At 322 K these values are: A μ (1)=606±2 MHz and A p (1)=108±2 MHz , for the muon on the opposite side of the ring from the cation; and A μ (2)=430±2 MHz and A p (2)=70±5 MHz , for the muon on the same side. These results as well as their trends with temperature demonstrate that the MuC6H6 radical adopts a non-planar equilibrium geometry due to the strong interaction of the π electron density with the Na cation.

The TRIUMF μSR user facility and data acquisition group have worked with Highland Technology to design a new generation of TDC useful for modern time-differential μSR. The result is the model B980 TDC marketed by BNC. It is an 8-channel VME clock with a timing resolution better than 100 ps incorporating an FPGA-based microengine, designed and coded at TRIUMF, to process the raw timing and ‘hit’ information to report only ‘good’ events (one start, one stop) allowing a high data rate, and making the TDC ideal for TD μSR.

In order to provide an assessment of the “global” accuracy of the Liu–Siegbahn–Truhlar–Horowitz (LSTH) potential surface for H3, hot atom reaction yields, which are determined from collision processes over an energy range much wider than that of single-collision experiments, have been calculated for the Mu*+H2 and T*+H2 systems. The isotopic comparison of muonium (Mu=μ+e−), an ultralight isotope of hydrogen (mMu/mH≈1/9), with the heaviest H-atom isotope, tritium, is a novel approach in testing the global accuracy of the H3 surface. These reaction yields have been calculated using a formalism developed for (μ+) charge exchange, with input cross sections for elastic, inelastic (rovibrational excitation) and reactive collisions determined from quasi classical trajectories on the LSTH surface, in the center-of-mass energy range 0.5–11 eV. The rate of energy loss of the hot atom (Mu* or T*) due to elastic and inelastic collisions with the moderator (H2) drastically affects the hot atom reaction yield. In parti...

The recombination reaction Mu+NO+M⇌MuNO+M (M=He, N2, CH4) has been studied by the muon spin relaxation/rotation (μSR) technique up to 520 bar at room temperature. The reaction remains in the low pressure regime throughout. The measured termolecular addition rate constant in N2, 8.8±0.3×10−33 cm6 s−1, is essentially the same as that found in our earlier study at pressures below 60 bar [J. J. Pan et al., J. Phys. Chem., 1995, 99, 17160]. It is somewhat smaller in He, 7.7±1.0×10−33, but larger in CH4, 12.8±2.0×10−33. The Mu+NO reaction is about five times slower than the corresponding H+NO reaction. The strong collision limits of the rate constants for three H-isotopes (Mu, H, D) reacting with NO have been estimated with Troe's formalism for unimolecular dissociation in the low pressure regime, based on the ab initio potential energy surface of Guadagnini et al. [J. Chem. Phys., 1995, 102, 774]. The Troe calculations give less than satisfactory agreement with experiment with the corresponding weak collision factor, βc , higher than expected by a factor of ∽2 for H+NO. The calculated kinetic isotope effect in the strong collision limit for Mu/H is weaker than the measured effect by a factor of two giving an apparent large isotope effect in this factor, βcMu≈½βcH, possibly due to mode specific collisional stabilization.

The rate constant of the gas-phase addition reaction of the light hydrogen isotope muonium to molecular oxygen, Mu + O2 → MuO2, was measured over a range of temperatures from 115 to 463 K at a pressure of 2 bar and from 16 to 301 bar at room temperature, using N2 as the moderator gas. The reaction remains in the termolecular regime over the entire pressure range. At room temperature, the average low-pressure limiting rate constant is kch0(Mu) = (8.0 ± 2.1) × 10-33 cm6 s-1, a factor of almost 7 below the corresponding rate constant for the H + O2 addition reaction, kch0(H). In contrast to kch0(H), which exhibits a clear negative temperature dependence, kch0(Mu) is essentially temperature independent. At room temperature, the kinetic isotope effect (KIE) is strongly pressure (density) dependent and is reversed at pressures near 300 bar. The kinetics are analyzed based on the statistical adiabatic channel model of Troe using a Morse potential, which works well in reproducing the overall KIE. The major factor...

The thermal reaction Mu + N2O has been studied by the muon spin rotation (μSR) technique at temperatures from 303 to 593 K and pressures up to 60 atm. The overall reaction rate coefficient depends ...

Muon spin rotation (μSR) and avoided level crossing resonance (ALCR) have been used to determine the hyperfine coupling constants (hfcs) of the muonium-substituted cyclohexadienyl radicals C6H6Mu, C6D6Mu and C6F6Mu in the gas phase, at pressures ∼1 and 15 atm and temperatures in the range 40–80°C. Equivalent studies of polyatomic free radicals in gases, by electron spin resonance (ESR) spectroscopy, are generally not possible in this pressure range. The present gas phase results support the findings of earlier studies of cyclohexadienyl radicals in the condensed phase, by both μSR and ESR. Minor but not insignificant (∼1%) effects on the hfcs are observed, which can be qualitatively understood for such nonpolar media in terms of their differing polarizabilities. This is the first time that comparisons of this nature have been possible between different phases at the same temperatures. These μSR/ALCR gas-phase results provide a valuable benchmark for computational studies on radicals, free from possible effects of solvent or matrix environments.

We report muon spin rotation measurements in n-type silicon from 10 to 310K in electric fields up to 5kV/cm. These experiments reveal the nature of the partition of neutral muonium centers into {ital normal muonium} (Mu{sup 0}{sub T}) and {ital anomalous muonium} (Mu{sup 0}{sub BC}): Formation of Mu{sup 0}{sub T} is consistent with {ital epithermal} processes prior to thermalization, while Mu{sup 0}{sub BC} is formed via electron transport to a {ital thermalized} positive muon. The spatial distribution of the excess electrons created in the {mu}{sup +} ionization track is shown to be anisotropic with respect to the muon. {copyright} {ital 1997} {ital The American Physical Society}

The spin relaxation of Mu was measured in mixtures of CO and Ar at pressures up to 270 atm and at various magnetic fields. The relaxation rate increased with magnetic field in the way expected for electron spin‐exchange processes, though the effect declined at high pressures. We describe the results in terms of spin relaxation of Mu‐formyl radicals, MuCO, which break up to give depolarized Mu at low pressures, but are increasingly stabilized at higher pressures.

ALC μSR spectra of the muonated ethyl and cyclohexadienyl radicals in the gas phase are reported. They have surprisingly narrow lines for a magnetic resonance type technique under conditions near ambient temperature and near 1 atmosphere pressure. The main reason for this behaviour is the dramatic reduction of electron spin relaxation in high magnetic fields.

Muon spin relaxation has been measured in longitudinal magnetic fields for Mu+CO and Mu+N2O reactions. The interpretation of the results for these small molecules, which are quite different than those obtained in larger molecule systems (e.g., Mu‐ethyl and Mu‐t‐butyl radicals), are made with the phenomenological model for Mu‐radical spin relaxation previously proposed. Proper fitting procedures are important in these cases and are discussed in the present paper.

The TRIUMF μSR facility is described. An overview is given of beam line characteristics, μSR spectrometers, experimental “inserts” and how they combine for various experiments. Some of the recent installations and future plans of the TRIUMF facility will be further highlighted. These include low background cryostat inserts, newly‐planned spectrometers, and the possibility of an additional beam line. The CAMP slow‐controls system for monitoring and controlling peripheral devices is outlined.

The spin relaxation of the muonium‐substituted ethyl radical (MuCH2ĊH2) and its deuterated analog (MuCD2ĊD2) has been studied in the gas phase in both transverse and longitudinal magnetic fields spanning the range ∼0.5–35 kG, over a pressure range from ∼1–16 atm at ambient temperature. The Mu13CH213ĊH2 radical has also been investigated, at 2.7 atm. For comparison, some data is also reported for the MuCH2Ċ(CH3)2 (Mu‐t‐butyl) radical at a pressure of 2.6 atm. This experiment establishes the importance of the μSR technique in studying spin relaxation phenomena of polyatomic radicals in the gas phase, where equivalent ESR data is sparse or nonexistent. Both T1 (longitudinal) and T2 (transverse) μSR relaxation rates are reported and interpreted with a phenomenological model. Relaxation results from fluctuating terms in the spin Hamiltonian, inducing transitions between the eigenstates assumed from an isotropic hyperfine interaction. Low‐field relaxation is primarily due to the electron, via both the nuclear h...