Positronium reemission yield from mesostructured silica films

Liszkay, L.; Corbel, C.; Pérez, P.; Desgardin, P.; Barthe, M.F.; Ohdaira, Toshiyuki; Suzuki, Ryoichi; Crivelli, P.; Gendotti, U.; Rubbia, A.; Etienne, Mathieu; Walcarius, Alain

doi:10.1063/1.2844888

Cited by 78 publications

(71 citation statements)

References 17 publications

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“…This work has also led to the use of thin mesoporous films that can be used as Ps converters [109,110,[246][247][248][279][280][281][282][283][284]. These materials produce Ps in a similar way to the powders discussed previously [35,36].…”

Section: Ps Productionmentioning

confidence: 99%

“…The Ps atoms are energetically inhibited from re-entering the bulk material, and experience a short-range force repelling them from the grain surfaces [245], keeping them mostly in the voids. This concept, with some modification, is important also in modern beam experiments that use thin mesoporous films to produce cold Ps atoms in vacuum [109,246,247], as well as in Ps porosimitry methods [248,249]. The work function φ Ps , of Ps formed in this way is given by…”

Section: Ps Productionmentioning

confidence: 99%

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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: Ps Productionmentioning

confidence: 99%

Section: Ps Productionmentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

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“…Positron annihilation spectroscopy (PAS) exploits this property to measure the type and concentration of vacancies in metals and semiconductors [2]. By measuring the lifetime of Ps, the distribution of open volume has been studied in porous SiO 2 [3,4], polymers [5], and biostructures [6].…”

Section: Introductionmentioning

confidence: 99%

Full-correlation single-particle positron potentials for a positron and positronium interacting with atoms

2014

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In this work we define single-particle potentials for a positron and a positronium atom interacting with light atoms (H, He, Li and Be) by inverting a single-particle Schrödinger equation. For this purpose, we use accurate energies and positron densities obtained from the many-body wavefunction of the corresponding positronic systems. The introduced potentials describe the exact correlations for the calculated systems including the formation of a positronium atom. We show that the scattering lengths and the low-energy s-wave phase shifts from accurate many-body calculations are well accounted for by the introduced potential. We also calculate self-consistent two-component density-functional theory positron potentials and densities for the bound positronic systems within the local density approximation. They are in a very good agreement with the many-body results, provided that the finite-positron-density electron-positron correlation potential is used, and they can also describe systems comprising a positronium atom. We argue that the introduced single-particle positron potentials defined for single molecules are transferable to the condensed phase when the inter-molecular interactions are weak. When this condition is fulfilled, the total positron potential can be constructed in a good approximation as the superposition of the molecular potentials.

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“…These pulses have Gaussian spatial distributions with full width at half maxima (FWHM) of ∼3 mm on target, and are < 5 ns in duration. The positrons are accelerated to 2.5 keV and implanted into a porous silica (SiO 2 ) film [16] in a magnetic field of 13 mT. Ps atoms are produced with an efficiency of ∼30% and a mean kinetic energy of ∼50 meV [17].…”

mentioning

confidence: 99%

Controlling Positronium Annihilation with Electric Fields

et al. 2015

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We show that the annihilation dynamics of excited positronium (Ps) atoms can be controlled using parallel electric and magnetic fields. To achieve this, Ps atoms were optically excited to n ¼ 2 sublevels in fields that were adjusted to control the amount of short-lived and long-lived character of the resulting mixed states. Inclusion of the former offers a practical approach to detection via annihilation radiation, whereas the increased lifetimes due to the latter can be exploited to optimize resonance-enhanced two-photon excitation processes (e.g., 1 3 S → 2 3 P → nS=nD), either by minimizing losses through intermediate state decay, or by making it possible to separate the excitation laser pulses in time. In addition, photoexcitation of mixed states with a 2 3 S 1 component represents an efficient route to producing long-lived pure 2 3 S 1 atoms via single-photon excitation. DOI: 10.1103/PhysRevLett.115.183401 PACS numbers: 36.10.Dr, 78.70.Bj Positronium (Ps) is an atomic system composed of an electron bound to a positron and has several unique properties, the most striking of which are its low mass (M Ps ¼ 2m e ) and the fact that it can decay through various annihilation pathways [1]. Electron-positron annihilation requires overlap of the particle wave functions [2] and in Ps is therefore dependent on the square of the radial wave function at the origin. This is zero for states with l > 0 [3]. Higher order annihilation processes can occur for states with l > 0 but are strongly suppressed [4] and in practice direct Ps annihilation occurs only from the ground 1 1 S 0 and 1 3 S 1 , and metastable 2 1 S 0 and 2 3 S 1 levels. The inhibition of Ps annihilation in states with l > 0 is the basis for several proposed schemes to manipulate annihilation rates using resonant and nonresonant laser fields [5][6][7][8][9][10][11]. More complex strategies have also been suggested [12,13], although these have also not yet been experimentally demonstrated.The radiative decay and annihilation time scales in the n ¼ 2 manifold in Ps span an enormous range: The 2 1 S 0 level is radiatively metastable, fluorescing on a time scale of ≃0.24 s [3], but annihilating in 1 ns; conversely the 2 3 P 0;1;2 levels decay by fluorescence to the 1 3 S 1 state in 3.19 ns, but their annihilation lifetimes exceed 100 μs [4]. The 2 3 S 1 level is also metastable and fluoresces in ≃0.24 s, but has an annihilation lifetime of ∼1.14 μs [1]. It is the disparate properties of these states that make the approach described here to manipulating decay rates particularly effective.We report the results of experiments in which Ps annihilation rates in a weak magnetic field are manipulated using parallel electric fields. This combination of fields permits control over the spin multiplicity and orbital angular momentum character of the n ¼ 2 sublevels accessible by single-photon excitation from the 1 3 S 1 ground state. By increasing the 2 1 P character of mixed states in the fields, radiative decay to the short-lived singlet ground state (1 1 S 0 ) can be...

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Positronium reemission yield from mesostructured silica films

Cited by 78 publications

References 17 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Full-correlation single-particle positron potentials for a positron and positronium interacting with atoms

Controlling Positronium Annihilation with Electric Fields

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