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Jones ACL, Greaves RG, Codding CL, Selim FA. Development of a pulsed, variable-energy positron beam for atomic scale defect studies. Rev Sci Instrum 2022; 93:043903. [PMID: 35489933 DOI: 10.1063/5.0077750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Positron annihilation spectroscopy provides a sensitive means of non-destructive characterization of materials, capable of probing single atom vacancies in solids with 10-7 sensitivity. We detail here the development of a magnetically guided, variable energy, pulsed positron beam designed to conduct depth-dependent defect studies in metals, semiconductors, and dielectrics, which will be the first of its kind in the United States. The design of the target stage provides capabilities for measurements during in situ annealing up to 800 °C and incorporates a new approach to minimize the background due to energetic backscattered positrons. The developed beam at Bowling Green State University provides a powerful tool for characterization of thin films, devices, and ion irradiated materials.
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Affiliation(s)
- A C L Jones
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, Ohio 43402, USA
| | - R G Greaves
- Department of Physics and Astronomy, University of California Riverside, Riverside, California, 92507, USA
| | - C L Codding
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43402, USA
| | - F A Selim
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, Ohio 43402, USA
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2
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Jones ACL, Moxom J, Fuentes-Garcia M, Cecchini GG, Membreno EE, Roeder EE, Mills AP. A resistive-anode based position-sensitive Rydberg atom detector. Rev Sci Instrum 2022; 93:013305. [PMID: 35104976 DOI: 10.1063/5.0077037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
We describe here the development and characterization of a position-sensitive detector for Rydberg atom experiments. The detector builds on an earlier design that field-ionized incident Rydberg positronium (Ps) atoms and then electrostatically focused the freed positrons onto a micro-channel plate (MCP) detector without the use of a position sensitive anode. In this design, pulses from the MCP are deposited onto a resistive anode, providing a means of measuring the incident particles' x, y positions. The first detector constructed utilized a pair of MCPs in a chevron configuration and was used to observe the focusing of Rydberg Ps atoms from an electrostatic mirror. A second detector, developed for use in a measurement of the 1S-2S interval of Ps, incorporates three MCPs in a Z-stack configuration to produce larger pulses. Using a UV-induced signal, we have characterized the performance of the assembled detectors, finding a spatial resolution of ∼1.4 mm for the largest induced pulses and for pulse widths of ∼7-10 ns FWHM; pulse times can be resolved to better than 1 ns. The Ps induced signal is anticipated to yield pulses ∼5 times larger, which are expected to achieve a spatial resolution of <1 mm. Appropriate lenses could make possible applications involving either imaging a large area or magnifying a small area of the incident Ps spatial distribution.
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Affiliation(s)
- A C L Jones
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - J Moxom
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - M Fuentes-Garcia
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - G G Cecchini
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - E E Membreno
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - E E Roeder
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A P Mills
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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Agarwal S, Liedke MO, Jones ACL, Reed E, Kohnert AA, Uberuaga BP, Wang YQ, Cooper J, Kaoumi D, Li N, Auguste R, Hosemann P, Capolungo L, Edwards DJ, Butterling M, Hirschmann E, Wagner A, Selim FA. A new mechanism for void-cascade interaction from nondestructive depth-resolved atomic-scale measurements of ion irradiation-induced defects in Fe. Sci Adv 2020; 6:eaba8437. [PMID: 32832684 PMCID: PMC7439404 DOI: 10.1126/sciadv.aba8437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 06/16/2020] [Indexed: 06/11/2023]
Abstract
The nondestructive investigation of single vacancies and vacancy clusters in ion-irradiated samples requires a depth-resolved probe with atomic sensitivity to defects. The recent development of short-pulsed positron beams provides such a probe. Here, we combine depth-resolved Doppler broadening and positron annihilation lifetime spectroscopies to identify vacancy clusters in ion-irradiated Fe and measure their density as a function of depth. Despite large concentrations of dislocations and voids in the pristine samples, positron annihilation measurements uncovered the structure of vacancy clusters and the change in their size and density with irradiation dose. When combined with transmission electron microscopy measurements, the study demonstrates an association between the increase in the density of small vacancy clusters with irradiation and a remarkable reduction in the size of large voids. This, previously unknown, mechanism for the interaction of cascade damage with voids in ion-irradiated materials is a consequence of the high porosity of the initial microstructure.
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Affiliation(s)
- S Agarwal
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
| | - M O Liedke
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - A C L Jones
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
| | - E Reed
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
| | - A A Kohnert
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - B P Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Y Q Wang
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - J Cooper
- Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27607, USA
| | - D Kaoumi
- Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27607, USA
| | - N Li
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - R Auguste
- Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - P Hosemann
- Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - L Capolungo
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - D J Edwards
- Nuclear Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - M Butterling
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - E Hirschmann
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - A Wagner
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
| | - F A Selim
- Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
- Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403, USA
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Cecchini GG, Jones ACL, Fuentes-Garcia M, Adams DJ, Austin M, Membreno E, Mills AP. Detector for positronium temperature measurements by two-photon angular correlation. Rev Sci Instrum 2018; 89:053106. [PMID: 29864868 DOI: 10.1063/1.5017724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report on the design and characterization of a modular γ-ray detector assembly developed for accurate and efficient detection of coincident 511 keV back-to-back γ-rays following electron-positron annihilation. Each modular detector consists of 16 narrow lutetium yttrium oxyorthosilicate scintillators coupled to a multi-anode Hamamatsu H12700B photomultiplier tube. We discuss the operation and optimization of 511 keV γ-ray detection resulting from testing various scintillators and detector arrangements concluding with an estimate of the coincident 511 keV detection efficiency for the intended experiment and a preliminary test representing one-quarter of the completed array.
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Affiliation(s)
- G G Cecchini
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A C L Jones
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - M Fuentes-Garcia
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - D J Adams
- College of Natural and Agricultural Sciences Machine Shop, University of California, Riverside, California 92521, USA
| | - M Austin
- Department of Physics, Marquette University, Milwaukee, Wisconsin 53233, USA
| | - E Membreno
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A P Mills
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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Jones ACL, Moxom J, Rutbeck-Goldman HJ, Osorno KA, Cecchini GG, Fuentes-Garcia M, Greaves RG, Adams DJ, Tom HWK, Mills AP, Leventhal M. Focusing of a Rydberg Positronium Beam with an Ellipsoidal Electrostatic Mirror. Phys Rev Lett 2017; 119:053201. [PMID: 28949762 DOI: 10.1103/physrevlett.119.053201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Indexed: 06/07/2023]
Abstract
Slow atoms in Rydberg states can exhibit specular reflection from a cylindrical surface upon which an azimuthally periodic potential is imposed. We have constructed a concave mirror of this type, in the shape of a truncated oblate ellipsoid of revolution, which has a focal length of (1.50±0.01) m measured optically. When placed near the center of a long vacuum pipe, this structure brings a beam of n=32 positronium (Ps) atoms to a focus on a position sensitive detector at a distance of (6.03±0.03) m from the Ps source. The intensity at the focus implies an overall reflection efficiency of ∼30%. The focal spot diameter (32±1) mm full width at half maximum is independent of the atoms' flight times from 20 to 60 μs, thus indicating that the mirror is achromatic to a good approximation. Mirrors based on this principle would be of use in a variety of experiments, allowing for improved collection efficiency and tailored transport or imaging of beams of slow Rydberg atoms and molecules.
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Affiliation(s)
- A C L Jones
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - J Moxom
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - H J Rutbeck-Goldman
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - K A Osorno
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - G G Cecchini
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - M Fuentes-Garcia
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - R G Greaves
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - D J Adams
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - H W K Tom
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A P Mills
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - M Leventhal
- Department of Astronomy University of Maryland, College Park, Maryland 20742, USA
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Jones ACL, Rutbeck-Goldman HJ, Hisakado TH, Piñeiro AM, Tom HWK, Mills AP, Barbiellini B, Kuriplach J. Angle-Resolved Spectroscopy of Positronium Emission from a Cu(110) Surface. Phys Rev Lett 2016; 117:216402. [PMID: 27911545 DOI: 10.1103/physrevlett.117.216402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Indexed: 06/06/2023]
Abstract
The affinity A_{Ps} of positronium (Ps) atoms for a metal is the negative of the maximum kinetic energy with which Ps is emitted into vacuum when thermalized positrons in a metal encounter the surface. When this quantity is measured by ground state Ps time of flight (TOF), the precision is severely limited by the short triplet state lifetime of 142 ns. By quickly converting the emitted Ps atoms into long-lived Rydberg states, we are able to dramatically increase the TOF to allow precision measurements of A_{Ps}. From our measurements made on a Cu(110) sample at T=128 K, we find A_{Ps}(128 K)=(-2.476±0.010_{stat}±0.013_{syst}) eV, compared with the result A_{Ps}(128 K)=(-2.545±0.010_{num}±0.010_{syst}) eV found using highly accurate generalized gradient approximations for both electrons and positrons within density functional theory. Such precision opens up opportunities in the quest for an improved density functional.
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Affiliation(s)
- A C L Jones
- Department of Physics and Astronomy, University of California Riverside, Riverside, California 92521, USA
| | - H J Rutbeck-Goldman
- Department of Physics and Astronomy, University of California Riverside, Riverside, California 92521, USA
| | - T H Hisakado
- Department of Physics and Astronomy, University of California Riverside, Riverside, California 92521, USA
| | - A M Piñeiro
- Department of Physics and Astronomy, University of California Riverside, Riverside, California 92521, USA
| | - H W K Tom
- Department of Physics and Astronomy, University of California Riverside, Riverside, California 92521, USA
| | - A P Mills
- Department of Physics and Astronomy, University of California Riverside, Riverside, California 92521, USA
| | - B Barbiellini
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
| | - J Kuriplach
- Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, CZ-180 00 Prague, Czech Republic
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Jones ACL, Piñeiro AM, Roeder EE, Rutbeck-Goldman HJ, Tom HWK, Mills AP. Large-area field-ionization detector for the study of Rydberg atoms. Rev Sci Instrum 2016; 87:113307. [PMID: 27910370 DOI: 10.1063/1.4967305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We describe here the development and characterization of a micro-channel plate (MCP) based detector designed for the efficient collection and detection of Rydberg positronium (Ps) atoms for use in a time-of-flight apparatus. The designed detector collects Rydberg atoms over a large area (∼4 times greater than the active area of the MCP), ionizing incident atoms and then collecting and focusing the freed positrons onto the MCP. Here we discuss the function, design, and optimization of the device. The detector has an efficiency for Rydberg Ps that is two times larger than that of the γ-ray scintillation detector based scheme it has been designed to replace, with half the background signal. In principle, detectors of the type described here could be readily employed for the detection of any Rydberg atom species, provided a sufficient field can be applied to achieve an ionization rate of ≥108/s. In such cases, the best time resolution would be achieved by collecting ionized electrons rather than the positive ions.
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Affiliation(s)
- A C L Jones
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A M Piñeiro
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - E E Roeder
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - H J Rutbeck-Goldman
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - H W K Tom
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A P Mills
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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Jones ACL, Goldman HJ, Zhai Q, Feng P, Tom HWK, Mills AP. Monoenergetic positronium emission from metal-organic framework crystals. Phys Rev Lett 2015; 114:153201. [PMID: 25933312 DOI: 10.1103/physrevlett.114.153201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Indexed: 06/04/2023]
Abstract
Recently it has been discovered that positronium (Ps), after forming in metal-organic framework (MOF) crystals, is emitted into vacuum with a high efficiency and low energy that can only be explained by its propagating as delocalized Bloch states. We show that the Ps atoms are emitted from MOFs in a series of narrow energy peaks consistent with Ps at Bloch-state energy minima being emitted adiabatically into the vacuum. This implies that the Ps emission energy spectra can be directly compared with calculations to obtain detailed information about the Ps band structure in the MOF crystal. The narrow energy width of the lowest energy Ps peak from one MOF sample (2-Methylimidazole zinc salt ZIF-8) suggests it originates from a polaronic Ps surface state. Other peaks can be assigned to Ps with an effective mass of about twice that of bare Ps. Given the immense catalog of available MOF crystals, it should be possible to tune the Ps properties to make vastly improved sources with high production efficiency and a narrow energy spread, for use in fundamental physics experiments.
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Affiliation(s)
- A C L Jones
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - H J Goldman
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Q Zhai
- Materials Science and Engineering Program and Department of Chemistry, University of California, Riverside, California 92521, USA
| | - P Feng
- Materials Science and Engineering Program and Department of Chemistry, University of California, Riverside, California 92521, USA
| | - H W K Tom
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - A P Mills
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
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Jones ACL, Danielson JR, Natisin MR, Surko CM. Role of vibrational dynamics in resonant positron annihilation on molecules. Phys Rev Lett 2013; 110:223201. [PMID: 23767720 DOI: 10.1103/physrevlett.110.223201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Indexed: 06/02/2023]
Abstract
Vibrational Feshbach resonances are dominant features of positron annihilation for incident positron energies in the range of the molecular vibrations. Studies in relatively small molecules are described that elucidate the role of intramolecular vibrational energy redistribution into near-resonant multimode states, and the subsequent coupling of these modes to the positron continuum, in suppressing or enhancing these resonances. The implications for annihilation in other molecular species, and the necessary ingredients of a more complete theory of resonant positron annihilation, are discussed.
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Affiliation(s)
- A C L Jones
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
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Danielson JR, Jones ACL, Natisin MR, Surko CM. Comparisons of positron and electron binding to molecules. Phys Rev Lett 2012; 109:113201. [PMID: 23005624 DOI: 10.1103/physrevlett.109.113201] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Indexed: 06/01/2023]
Abstract
Positron binding to molecules is compared to the analogous electron-molecule bound states. For both, the bound lepton density is diffuse and remains outside the valence shell. Positron binding energies are found to be one to two orders of magnitude larger than those of the negative ions due to two effects: the orientation of the molecular dipole moment allows the positron to approach it more closely and, for positrons, lepton correlations (e.g., via dipole polarizability) contribute more strongly.
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Affiliation(s)
- J R Danielson
- Department of Physics, University of California at San Diego, La Jolla, California 92093, USA
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Jones ACL, Danielson JR, Natisin MR, Surko CM, Gribakin GF. Ubiquitous nature of multimode vibrational resonances in positron-molecule annihilation. Phys Rev Lett 2012; 108:093201. [PMID: 22463631 DOI: 10.1103/physrevlett.108.093201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Indexed: 05/31/2023]
Abstract
Positron annihilation on many molecules occurs via positron capture into vibrational Feshbach resonances, with annihilation rates often further enhanced by energy transfer to vibrational excitations weakly coupled to the positron continuum. Data presented here uncover another scenario in which the positron couples directly to a quasicontinuum of multimode vibrational states. A model that assumes excitation and escape from a statistically complete ensemble of multimode vibrations is presented that reproduces key features of the data.
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Affiliation(s)
- A C L Jones
- Physics Department, University of California, San Diego, La Jolla California 92093, USA
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Jones ACL, Caradonna P, Makochekanwa C, Slaughter DS, McEachran RP, Machacek JR, Sullivan JP, Buckman SJ. Observation of threshold effects in positron scattering from the noble gases. Phys Rev Lett 2010; 105:073201. [PMID: 20868040 DOI: 10.1103/physrevlett.105.073201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Indexed: 05/29/2023]
Abstract
Channel coupling is a phenomenon that has been investigated for many scattering processes, and is responsible for the formation of cusps or steps in the cross sections for open scattering channels at, or near, the onset of a new scattering channel. It has long been speculated that the opening of the positronium formation channel may lead to the formation of such cusp features in the elastic positron scattering cross section. In this work, elastic scattering of positrons has been measured in the region of the positronium formation threshold for the noble gases He-Xe. Cusplike behavior is observed and, while the features which are observed appear broad, they represent a magnitude of between 4 and 15% of the total elastic cross section. No evidence is found of any other features in this region, at least within the uncertainty of the present data, discounting the possibility of scattering resonances.
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Affiliation(s)
- A C L Jones
- ARC Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, Australian National University, Canberra 0200 Australia
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