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Showing 1 to 20 of 24 for “"Positronium"”.
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On the reactions of ortho-positronium and inhibition of positronium formation
A study of the interactions of ortho-positronium with a variety of inorganic and organic compounds was undertaken to investigate the mechanisms of the thermal reactions of ortho-positronium and to investigate the processes which inhibit positronium formation. It was found that the rate constants …
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The first excited state of positronium
Thesis (Ph.D.) Massachusetts Institute of Technology. Dept. of Physics, 1955.
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Magnetic quenching of positronium in n-pentane
Submitted by William Weathers (weathrs2@illinois.edu) on 2012-03-21T17:01:25Z No. of bitstreams: 1 1971_henkin.pdf: 944651 bytes, checksum: 1bd22d9c5a5158c1b37c728fc95b998f (MD5)
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Multi-photon decay mode spectroscopy of positronium
… branching ratio of the four-photon decay of parapositronium (BR4γ) was measured using a multi-gamma-ray spectrometer. For the first time in such measurements, the spectrometer consisted of an array of eight identical LaBr3:Ce scintillator detectors, each of which combines good energy resolutions …
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Measurement of the Decay Rate of the Negative Positronium Ion
… positron and two electrons, the negative ion of positronium is one of the simplest three-body systems with a bound state. Its constituents are stable, point-like particles, and due to the small particle masses, it is essentially free from perturbations by strong interaction effects. Together with …
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The reaction of ortho-positronium with nitroaromatics via complex formation
… made to ascertain the mechanism by which ortho-positronium reacts with nitroaromatics in solution. These reactions are two to three orders of magnitude faster than expected by simple pickoff. Conjugation of the nitro group with the aromatic ring was found to be a necessary condition for this …
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GEANT4-based model and experimental validation of positronium lifetime in organic and inorganic materials
Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-05-01
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Positronium complex formation: mechanisms, solvent effects and its application to the study of molecular phenomena
… “exotic atoms" in Chemistry and Physics is positronium. Positronium (Ps) is the bound state of an electron and positron. It is formed in two ground states, para-positronium (p-Ps) and ortho-positronium (o-Ps) whose lifetimes in free space are 0.125 nsec and 140 nsec respectively. When …
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Positronium formation in organic liquids and studies of micelle, liposome and polymer systems by position annihilation technique
… can interact with an electron resulting in a positronium formation (Ps). In the first part of this thesis the formation of positronium in benzene solutions containing various halogenated compounds was studied in the presence and absence of C₆F₆ additives. The observed I₂ values, which are …
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Design of a positron beam for the study of the entanglement in three gamma-rays generated by positronium annihilation
… in the 1950s [9]. This bound state is called positronium (Ps) and it is the lightest bound matter-antimatter system. It is a hydrogen-like atom, with the positron substituting for the proton, this gives it particular properties [10]. The Ps is not stable, and, in its ground level, it is …
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Γεωμετρική προσέγγιση ανακατασκευής μέσω τριπλής σύμπτωσης στην πολυφωτονική απεικόνιση τύπου PET
… εργασίας είναι η μελέτη της διάσπασης του ortho-Positronium και η ανάπτυξη αλγορίθμου γεωμετρικής ανακατασκευής με τρία φωτόνια σε σύμπτωση. Αρχικά στα πέντε πρώτα κεφάλαια, αναλύεται το θεωρητικό υπόβαθρο. Ειδικότερα, το Kεφάλαιο 1 πραγματεύεται το θεωρητικό υπόβαθρο σχετικά με τις …
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Positronium in the AEgIS experiment: study on its emission from nanochanneled samples and design of a new apparatus for Rydberg excitations
… distribution of Ps emitted by a positron-positronium converter as well as its excitation in Rydberg states have to be studied and optimized. In this thesis Ps cooling and emission into vacuum from nanochannelled silicon targets was studied by performing Time of Flight measurements with a …
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Asymmetric Positron Annihilation in Chiral Tartrate and Tartaric Acid Crystals
… noted with the L- enantiomers exhibiting longer positronium lifetimes and lower intensities, signifying a more stable environment for the positron and positronium. Possible implications for the dominance of L-amino acids in living matter are discussed.
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Production and excitation of cold Ps for anti-H formation by charge exchange: towards a gravitational measurement on antimatter
… requires access to an abundant source of cold positronium which can be achieved by the employment of oxide-coated nanochanneled silica plates (NCPs). We spend chapter 1 formulating a classical model of positronium production and thermalisation in NCPs and validating it by testing it against the …
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Positron interactions with oriented polymers and with chiral quartz crystals
… a significant intensity difference in free positronium annihilation for left handed (LH) and right handed (RH) chiral quartz crystals. Doppler broadening energy spectra (DBES) of z-cut LH or RH quartz disks at different angles were also measured by an “S parameter” to probe the observed …
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Cold trapped positrons and progress to cold antihydrogen
… and demonstrated. Strongly magnetized Rydberg positronium is formed and then ionized, allowing us to trap equal numbers of either positrons or electrons over a wide range of conditions. Antiprotons are trapped, cooled, and stacked from the new Antiproton Decelerator facility for the first time. …
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A novel high-efficiency SiPM-based system for Ps-TOF
A novel set up for Positronium Time Of Flight is proposed, using Silicon Photomultipliers (SiPMs) instead of Photomultiplier Tubes. The solution allows us to dramatically increase the compactness of the set up, thus improving the efficiency of 240%. Different configurations of SiPM+scintillators …
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Some effects on polymers of low-energy implanted positrons
… and in polymeric materials is the emission of positronium (Ps) from the sample surface. In Doppler broadening of annihilation radiation (DBAR) experiments, it has been shown that in a longitudinal setup, the para-Ps (p-Ps) contribution to the photo-peak is detected as a narrow fly-away peak at …
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Simulation and Characterization of Single Photon Detectors for Fluorescence Lifetime Spectroscopy and Gamma-ray Applications
… for the study of the Time-Of-Flight (TOF) of Positronium (Ps) and the displacement of 2D array of CMOS SPADs in a lab-on-chip apparatus for Fluorescence Lifetime Spectroscopy. The two design procedures are performed using Monte-Carlo simulations. Characterizations of the two sensor have been …
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A comparative study of metrology techniques for porous organic thin films
… industrial use, involving radioactivity such as Positronium Annihilation Lifetime Spectroscopy and Small Angle Neutron Scattering. Atomic Force Microscopy is limited to surface analysis, and pores may be intersecting the surface at a variety of chords, not necessarily the diameter. Each of these …
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