Muonium Formation Research Articles

Track effects and muonium formation

Track effects and muonium formation

Participation of the OH radical in the terminal muon spur

The results of hydroxyl scavenging experiments are presented as further evidence in support of a spur model for muonium formation.

Radiolysis effects in muonium chemistry

The chemistry of muonium, a light isotope of hydrogen, is investigated for the time period immediately after stopping of its precursor, the positive muon, in the condensed phase. Information is extracted from the initial amplitudes of the muon precession signals arising from muonium and muon-substituted diamagnetic compounds. In liquid water part of the initial spin polarization cannot be accounted for in terms of existing models of muonium formation and reaction. This missing fraction is postulated to arise via a spin exchange interaction of muonium with a hydrated electron. It is also suggested that the chemical fate of the muon is determined by reactions with transient species created in the terminal spur of the muon track.

Production of thermal muonium in the vacuum between the grains of fine silica powders

When spin-polarized positive muons are stopped in fine SiO 2 powder under vacuum, muonium precession is observed indicating 45% muonium formation. Depolarization by oxygen indicates that muonium, like positronium, emerges from the powder grains into the voids.

Interaction of muonium with radiolysis products in pure water: OH· scavenging action by tert-butyl alcoholt

Abstract The effects of scavenging OH− radicals by alcohols on muonium formation when positive polarized muons are stopped in water are reported. The results suggest that muonium formation takes place dominantly by a “spur” mechanism.

Evidence of muonium formation using thin gold foils in vacuum

The production of thermal muonium in a vacuum region has been investigated using an array of 200 thin (\ensuremath{\sim}1000 \AA{} thick) gold foils exposed to a stopping ${\ensuremath{\mu}}^{+}$ beam. By examining the observed time dependence of the ${\ensuremath{\mu}}^{+}$-decay spectra in various transverse magnetic fields, we estimate that the lower limit of the probability of muonium formation by these gold foils placed in vacuum was 0.28\ifmmode\pm\else\textpm\fi{}0.05.

Theory and analysis of μ + spin polarization in chemical systems

A theoretical model is developed for the description of the time evolution of spin polarization of positive muons stopped in liquid systems of chemical interest. The formalism is applicable to reaction schemes describing formation and reaction of muonium and muonic radicals in both consecutive and competitive steps. Explicit analytical solutions are derived and these, or numerical solutions, may be used to simulate and analyse the results of transverse and longitudinal field μSR experiments. Reanalysis of earlier experimental results shows an ambiguity in the determination of two rate constants. Direct rate measurements are thus strongly recommended over inference of rate constants from residual polarization and phase. Finally experiments are proposed to settle the question of whether or not muon-electron spin correlation is disturbed during the reaction of muonium to form a muonic radical.

Muonium-formation measurement in low-pressure argon gas

Direct precession measurements of the muonium atomic system have been made in argon gas at low pressures of 1290 and 2280 Torr. At the higher pressure the probability of muonium formation was found to be (85 \ifmmode\pm\else\textpm\fi{} 9)%. This lower limit for the rate of formation is in agreement with that predicted by Firsov and Byakov on the basis of muonium energy thresholds.

Muonium Formation in Noble Gases and Noble-Gas Mixtures

In an experiment at the Clinton P. Anderson Meson Physics Facility, no muonium formation was found in pure He or Ne, and abundant formation in Ar and Xe. A small Xe admixture (0.1%) in He and Ne resulted in abundant muonium formation, due to the process in which Xe serves as an electron donor to a low-energy positive muon. These results are qualitatively consistent with our knowledge of relevant atomic collision cross sections.

Formation of muonium in fast collisions of mu+mesons with atomic systems

The process of muonium ( mu /sup +/,e) formation by electron capture mechanism in collisions of positive mesons with atomic systems is considered at high energies. The continuum distorted wave (CDW) method is used for calculation of the cross sections for mu /sup +/-H and mu /sup +/-He electron capture reactions from 10 keV to 1 MeV. The calculated cross sections are compared with those for electron capture from the same atomic systems by protons. (auth)

Muonium formation in slow collisions of positive mesons with hydrogen atoms

The process of muonium formation in slow collision of positive mesons with hydrogen atoms is considered in the energy range of 0.4 eV to 5 KeV using the adiabatical methods for near-resonant atomic reactions.

"Fast" Depolarization of Positive Muons in Solution-the Chemistry of Atomic Muonium

The initial magnitude and direction of the residual asymmetry in the decays of polarized positive muons stopped in solutions in transverse magnetic fields are observed to depend strongly upon the concentration of dissolved compounds. Such effects were seen in methanol solutions of ${\mathrm{I}}_{2}$ and in aqueous solutions of Fe${\mathrm{Cl}}_{3}$ and Fe(${\mathrm{CI}}_{4}$)${\mathrm{O}}_{3}$. The underlying fast depolarization mechanism can be qualitatively and quantitatively understood by assuming muonium formation with subsequent chemical reaction of the atomic muonium with dissolved compounds.

Muonium. I. Muonium Formation and Larmor Precession

A complete quantitative discussion is given of the experiments in which muonium was discovered through studies of the depolarization of muons in gases and of the Larmor precession of muonium in argon in a static magnetic field. Also described are the observation of the hfs interval $\ensuremath{\Delta}\ensuremath{\nu}$ of muonium in its ground state and the determination of $\ensuremath{\Delta}\ensuremath{\nu}$ to an accuracy of about 50% through the use of a static magnetic field. A theoretical discussion is given of muonium formation in gases, including polarization effects. The experimental results on the Larmor precession of muonium prove that close to 100% of the muons stopping in pure argon gas form muonium. The experimental results on muon depolarization in other gases, together with the theoretical considerations, suggest that abundant muonium formation should occur when muons are stopped in most gases; the case of S${\mathrm{F}}_{6}$ appears anomalous in that, at most, only small formation of muonium is indicated. A discussion of the energy levels and decay characteristics of muonium is given. This is the first in a series of papers on the muonium atom and on its interactions in gases.

Study of the quenching of muon depolarization in several materials as a function of externally applied magnetic fields

The results of a systematic study on the quenching of muon depolarization as a function of a variable magnetic field parallel to the original muon polarization are reported. The data obtained are relative to values of the magnetic field which range from 0 to 4 kG, and are compared with predictions of the various muonium formation theories.

Possible Electromagnetically Induced Muonium-An timuonium Conversion

The possibility of the existence of an electromagnetically induced transition between muonium and anti-muonium is examined. An experiment is suggested involving the formation of muonium by the injection of positive muons into a helium-filled resonant cavity, which is excited at a frequency corresponding to the difference in interaction energy between muonium and helium, on the one hand, and that between anti-muonium and helium, on the other. The sign of antimuonium formation is the observation of the fast electrons from ${\ensuremath{\mu}}^{\ensuremath{-}}$ decay. The dependence of the number of these on which of the various cavity modes is excited gives information on the relative intrinsic parity of muonium and antimuonium. If this turns out to be odd, then this measurement, when combined with the usual relation for the product of the intrinsic parities of a Dirac particle and its antiparticle, would determine the relative intrinsic parity of the muon and electron to be imaginary. The conservation of parity in electromagnetic phenomena and the absence of electromagnetic $\ensuremath{\mu}\ensuremath{-}e$ transitions would then both find their natural explanation in the single assumption that the observation of electromagnetic phenomena must be compatible with invariance under space inversion.

Muonium Formation in Semiconductors

The depolarization of muons in doped silicon, germanium, and graphite was studied by measuring the asymmetry in the angular distribution of positions from muon decay. The results are discussed in terms of muonium formation, and the effects of donor concentration on the formation are considered. (D.L.C.)

Formation of Muonium and Observation of its Larmor Precession

Formation of Muonium and Observation of its Larmor Precession

Paschen-Back Effect as a Means of Detecting Muonium

Although formation of muonium (the bound system of a ${\ensuremath{\mu}}^{+}$ meson and an electron) can be expected in suitable materials, the precession test for it has been negative. Since this test is sensitive to slight perturbations it is proposed to substitute for it a more positive and insensitive test which uses a strong magnetic field in the direction of the initial muon orientation rather than a weak field at right angles. In this way the depolarizing effect of the muonium hyperfine coupling is quenched and the beta-decay asymmetry will be increased. The amount of increase determines the fraction of muons forming muonium. For a field of five kilogauss the quenching should be 90% complete.