Resonant Scattering of Positronium in Collision with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>CO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Brawley, S. J.; Williams, AE; Shipman, M.; Laricchia, G.

doi:10.1103/physrevlett.105.263401

Cited by 43 publications

(44 citation statements)

References 35 publications

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“…A similar effect has already been observed in total scattering measurements between ground state Ps atoms with various atomic and molecular targets [640,641]. In some of these experiments Ps beam energies comparable to or higher than the Ps binding energy (6.8 eV) are used, allowing the interactions to be reasonably well characterized by the impulse approximation [642,643].…”

Section: Scatteringmentioning

confidence: 56%

Experimental progress in positronium laser physics

2018

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Abstract. The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥10 6 ) accumulated in such a device may be ejected all at once, so as to generate an intense pulse. Standard bunching techniques can produce pulses with ns (mm) temporal (spatial) beam profiles. These pulses can be converted into a dilute Ps gas in vacuum with densities on the order of 10 7 cm −3 which can be probed by standard ns pulsed laser systems. This allows for the efficient production of excited Ps states, including long-lived Rydberg states, which in turn facilitates numerous experimental programs, such as precision optical and microwave spectroscopy of Ps, the application of Stark deceleration methods to guide, decelerate and focus Rydberg Ps beams, and studies of the interactions of such beams with other atomic and molecular species. These methods are also applicable to antihydrogen production and spectroscopic studies of energy levels and resonances in positronium ions and molecules. A summary of recent progress in this area will be given, with the objective of providing an overview of the field as it currently exists, and a brief discussion of some future directions.

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Section: Scatteringmentioning

confidence: 56%

Experimental progress in positronium laser physics

2018

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“…RTE is analogous to the dielectronic recombination (DR) occurring in electron-atom collisions (the inverse process of the Auger decay); that is why the quasifree electron model is well suited for its description. As a further example, we mention the recent experimental investigations of the scattering of positronium (Ps) on atoms [8,9]. The obtained results suggest that the electron constituent of Ps plays the dominant role in the collision, and it interacts with the target as a quasifree particle: The measured total cross sections revealed an unexpected, strong similarity with those for equivelocity electron projectiles.…”

Section: Introductionmentioning

confidence: 71%

Multiple ionization of rare gases by hydrogen-atom impact

et al. 2013

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Cross sections for the multiple ionization of He, Ne, Ar, and Kr by H 0 impact with and without the simultaneous ionization (electron loss) of the projectile are presented in the energy range 75-300 keV. The data were measured by coincident detection of the recoil target ions and the charge-state analyzed scattered projectiles. To obtain information about the role played by the electron of H 0 in the collision, the measurements were repeated with protons under the same experimental conditions. The measured data are analyzed using the classical trajectory Monte Carlo (CTMC) method. CTMC describes well the experimental data for both projectiles for single vacancy creation; however, increasing deviation is observed between theory and experiment with increasing number of created vacancies and with decreasing target atomic number.

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“…values for the positron and Ps total cross-sections have been taken from available literature, specifically from [46][47][48][49] and [50][51][52] respectively, interpolating when necessary. At 120 eV for He and Ar, where Ps data were not available, the cross-sections were estimated by extrapolation, guided by the findings of Brawley et al [50] on the similarity with equivelocity-electron results.…”

Section: Psmentioning

confidence: 99%

Absolute Differential Positronium-Formation Cross Sections

et al. 2015

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The first absolute experimental determinations of the differential cross-sections for the formation of ground-state positronium are presented for He, Ar, H2 and CO2 near 0 ○ . Results are compared with available theories. The ratio of the differential and integrated cross-sections for the targets exposes the higher propensity for forward-emission of positronium formed from He and H2.PACS numbers: 36.10. Dr, 34.80.Bm, 34.80.Uv The formation of positronium (Ps, the bound state of an electron and a positron) is an important channel in the scattering of positrons from atoms and molecules e.g. [1][2][3], accounting for up to 50% of the total cross-section, with experimental and theoretical investigations of its integrated formation cross-sections available for a wide range of atoms and simple molecules, e.g. [3][4][5]. Recent experimental studies also include its formation in an excited state [6] or accompanied by ionic excitation [7]. However, whilst theoretical predictions for the differential Ps formation cross-section ( dQPs dΩ ) are available for atomic [8][9][10][11][12][13][14][15][16] and molecular [17,18] hydrogen, the noble gases [9,16,[19][20][21][22][23][24][25][26][27][28][29] Details of the experimental arrangement employed at UCL for producing a beam of Ps atoms, together with a review of recent advances, may be found in [41]. In brief, the Ps beam is produced by charge-exchange of positrons (e + ) with a target gas (A), i.e. e + + A → Ps + A + , and detected downstream by a channel-electronmultiplier (CEM or CEMA) in coincidence with one or more γ-ray detectors (e.g. CsI or NaI) where it has been found to be composed predominantly of groundstate atoms [42,43].Depending on the relative spin orientation of its constituents, ground-state Ps may be formed in an ortho-( 3 S 1 ) or para-( 1 S 0 ) state. The two are characterized by lifetimes differing by three orders of magnitude (142 ns and 125 ps, respectively) and different annihilation modes (dominantly 3-γ and 2-γ, respectively). Only ortho-Ps reaches the detection region.In order to determine dQPs dΩ (a measure of the probability that Ps is emitted within a solid angle dΩ = 2πsinθdθ), we have measured the number of Ps atoms (ε where τ Ps is the lifetime of ortho-Ps, t its flight-time to the detector and ǫ Ps the 'true' Ps beam production efficiency. In Eq.(1), ǫ m Ps may be seen to depend on the (energy-dependent) ratio of the positron to positronium detection efficiencies R d also determined by our group [38][39][40].By studying the variation of ǫ Ps with gas pressure, optimum beam operating conditions may be determined for a given target and Ps energy [39,40,44,45]. An example is shown in Figure 1 for production of 20 eV Ps from CO 2 . Here ǫ Ps may be seen to increase and then decrease with increasing pressure. This variation may be expressed as:

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Resonant Scattering of Positronium in Collision withCO2

Cited by 43 publications

References 35 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Multiple ionization of rare gases by hydrogen-atom impact

Absolute Differential Positronium-Formation Cross Sections

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