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Tuesday, July 21, 2020 | History

2 edition of Positron annihilation in liquid argon. found in the catalog.

Positron annihilation in liquid argon.

Dalia M. Spektor

Positron annihilation in liquid argon.

by Dalia M. Spektor

  • 91 Want to read
  • 13 Currently reading

Published .
Written in English

    Subjects:
  • Physics Theses

  • Edition Notes

    Thesis (M.Sc.), Dept. of Physics, University of Toronto.

    ContributionsPaul, D. A. L. (supervisor)
    The Physical Object
    Pagination32 p.
    Number of Pages32
    ID Numbers
    Open LibraryOL18924495M

    The second, third, and fourth virial coefficients for argon, methane, nitrogen, and xenon have been established by various methods to satisfy experimental compressibility data and also to satisfy graphical computations of the property deviation relationships of Δu o and Δh o. A positron is the antiparticle of an electron. It has the same mass but an opposite charge to that of the electron. Dirac introduced an idea of the positive electron in (Dirac, ), and, soon after, Anderson found it, that was the positron, in during observation of radiations from the universe, as shown in Figure (Anderson, ).

    The recent results obtained on the ion-irradiation-induced carbon nanostructures in optoelectronic polymer materials exemplified by boron-ion-implanted polymethylmethacrylate (B:PMMA) with an energy of 40 keV, ion doses from × to × ions/cm2, and current density positron annihilation spectroscopy (slow positron beam spectroscopy based on . Positron spur reactions with excess electrons and anions in liquid organic mixtures of electron acceptors. STUDY OF STRUCTURAL CHANGES IN MICELLAR SOLUTIONS AND MICROEMULSIONS BY POSITRON ANNIHILATION TECHNIQUES: THEIR RELEVANCE TO LIQUID SCINTILLATION COUNTING PHENOMENA1. Books and Reference; Advertising Media Kit; .

    Positron annihilation in room temperature samples of the molecular gases N2, O2, CO, N2O and CH4 has been studied in the density range below 10 amagat using the positron lifetime technique. Introduction Positron Annihilation in Chemistry History of Chemistry-Oriented Positron Annihilation Studies Review of Physics-Oriented Positron Research The Content and Intention of this Book Theory The Annihilation Probability Atomic Physics of Positronium (Ps) Application of the Theory


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Positron annihilation in liquid argon by Dalia M. Spektor Download PDF EPUB FB2

Positron Annihilation focuses on the process of positron annihilation in different environments. Partitioned into two parts with 42 chapters, the book contains the contributions of authors who have done research on the annihilation of positrons, which brought about valuable information on the properties of Edition: 1.

Gaseous positronics and positron annihilation in condensed gases and liquids are also discussed. The second part of the book focuses on developments on positron annihilation and the direction of research on this field. The studies concentrate on positron annihilation in various crystals, metals, mercury, liquefied gases, helium, and metal oxides.

Positron Annihilation in Metals. On the Theory of Positron Annihilation in Metals A. Stewart admixtures angular correlation curves angular distribution annihilation rate approximation argon benzene Berko Bisi bound bubble calculated Canad CCl4 Celitans collisions concentration conduction electrons core cross section About Google.

Conventional angular-correlation experiments were performed in several simple condensed media to study the effects of various physical and chemical processes on positronium (Ps) yields.

Momentum spectra were obtained with static magnetic fields applied to liquid helium, neon, argon, and nitrogen and to solid neon and argon. Experiments with electric fields applied and with O2 impurity Author: A.

Stewart, C. Briscoe, J. Steinbacher. Positron annihilation spectroscopy (PAS) or sometimes specifically referred to as Positron annihilation lifetime spectroscopy (PALS) is a non-destructive spectroscopy technique to study voids and defects in solids. Theory. A Feynman diagram of an electron and positron annihilating into a.

Therefore, the processes the characteristic time of which is less than lifetime of a positron in a medium have a lot of common features with the corresponding electron processes. For example, in dense gases and liquids positrons collide many times with atoms before annihilation.

The Positron annihilation in liquid argon. book rate, λ[sub e], of positrons in unsaturated, saturated and liquid argon has been measured over the temperature range of K to K with applied electric fields up to 40 V cm⁻¹ amagat⁻¹. The data was analysed in terms of the classical distribution for self-nucleating clusters which depends on the difference in chemical potential, Δg, between the gas state and.

Positron annihilation processes in a liquid scintillator to be used for the detection of electron antineutrinos in the KamLAND project were studied.

The liquid scintillator was a mixture of isoparaffin, pseudocumene and 2,5-diphenyloxazole. We measured positron annihilation lifetime (PAL) spectra which contained important timing. The annihilation rate in conduction electrons can be given by [7] ;kcond = where c~ is the fine structure constant, n = 2 for the number of free electrons per atom and ~2 is the aver- age atomic volume for liquid mercury.

The total annihilation rate of positrons in liquid mercury is then = X i09 sec1 which gives a mean positron lifetime of. Analyses of the Doppler-broadening energy spectra for positrons annihilating in solid and liquid Ni are reported. Comparisons are made among the momentum distributions of positron-electron pairs annihilating in the essentially defect-free lattice, the vacancy and the liquid state of Ni.

The increase in the free positron lifetime with field is less marked at K. In liquid argon measurements were made at the normal boiling point only, at fields up to 20 kV/cm, above which we experienced electrical breakdown.

The angular-correlation technique of positron annihilation has been used to detect and measure the localized bubble state of positronium (Ps) in liquid Ne, Ar, Kr, H 2, and N 2 and in liquid and solid He at various pressures and temperatures.

No bubble state was seen in liquid O 2 or in solid Ne and Ar. The dynamics of bubble formation is not yet understood.

is a simultaneous emission of a positron and a gamma ray, each with an energy equivalent to half of the muon mass, MeV, at an opening angle of o.

The gamma ray is detected by a liquid xenon photon detector, which is described in detail in this paper. A positron detector is composed of a drift chamber tracking system [5], time measuring. The lifetime spectra of positrons annihilating in gaseous NH 3, in NH 3 –Ar and NH 3 –Ne gas mixtures, and in liquid NH 3 have been measured as a function of density and temperature.

The annihilation rate of slow positrons in NH 3 gas, λ NH 3, has a strong nonlinear dependence on gas density and temperature, indicating a complex positron‐ammonia interaction. Positron annihilation method was applied to study phase transitions in argon intercalated n-nonadecane.

Particular phases are easily recognizable due to large differences in ortho-positronium lifetimes. It was found that melting temperature is a non-monotonous function of pressure. In the range of temperatures K with the rise of pressure the phase sequence rotator - liquid-rigid.

Positron Annihilation in Chemistry gives a critical review of the chemistry-oriented positron annihilation research. The only three light particles participating in low energy physics and chemistry are the electron, positron, and positronium.

Positronium (Ps) is the most important "anomalous" atom. Lifetime techniques have been used to measure the direct annihilation rate in Argon gas as a function of temperature. In order to accomplish this, a pressure chamber capable of holding 10 amagats of gas at °C was designed and constructed.

The temperature of the Argon gas was varied between °K and °K. The results were collected at specific temperatures for gas densities of and.

Positron lifetimes have been measured, as a function of temperature, in the following liquid crystalline substances: cholesteryl benzoate, cholesteryl stearate, cholesteryl myristate, and p‐azoxyanisole. The value of τ 2 was observed to vary at the melting point of each compound and at smectic transitions.

No change in τ 2 occurred at nematic isotropic and cholesteric isotropic transitions. Positron annihilation lifetime spectra for n-nonadecane in nitrogen atmosphere were measured as a function of pressure and temperature and compared with similar results for argon atmosphere.

The positron lifetime measurements have been performed as a function of temperature for liquid methane and propane and as a function of magnetic field for liquid argon.

The long o-Ps lifetime, high o-Ps intensity, and a strong temperature dependence of these values are observed, and interpreted as being due to the Ps localization in the bubble.

Over the whole density range, the ortho-positronium annihilation rate was found to depend linearly on density, with a value of ± μs −1 for the vacuum rate of ortho-positronium annihilation and ± μs −1 amagat −1 for the quenching rate of positronium in argon.The volumes present over reviewed papers on the present state of the art and future prospects in the wide field of research involving positrons.

The foreword by Edward Teller and the summaries by Jean-Charles Abbe (Chemistry) and Alfred Seeger (Physics) demonstrate how the field is seen from "outside" and from "inside".Surface tension is an important property of liquid, the bulk surface tension concept changes considerably when minute volume of a given liquid (drop let radius.