Binding-energy predictions of positrons and atoms

Cheng, Xiang; Babikov, Dmitri; Schrader, D. M.

doi:10.1103/physreva.83.032504

Cited by 26 publications

(19 citation statements)

References 28 publications

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“…There now exist many predictions of positron-atom binding for a wide variety of atoms [629][630][631], but there is still no experimental evidence for these states whatsoever. This is largely because one needs a mechanism to attach the positron to an atom, and also because those species that are expected to bind positrons are experimentally difficult to work with (for example, a hot cell may be required).…”

Section: Scatteringmentioning

confidence: 99%

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: 99%

Experimental progress in positronium laser physics

2018

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“…Mitroy, in 2004 [11], estimated the exact ground state of the system at À7:532 895 5 hartree and a binding energy of 0.002 484 hartree using a large SVM calculation with 1200 explicitly correlated Gaussians. To our knowledge this is the current best estimate of the total and binding energy of this system.Although an experimental observation is still lacking and all the evidence comes from extensive calculations, at least 11 neutral atoms are supposed to bind a positron in their ground state [12,13]. In contrast, very few computational studies have been performed on excited states, and this is unfortunate since the existence of excited states of positronic atoms could provide a path to the experimental observation of these systems, similarly to what happened with the recent experimental observation of the dipositronium molecule [14] exploiting the existence of an excited state.Given the importance of lithium in establishing a definitive theoretical proof that a neutral atom can bind a positron, it is surprising that there are no published studies on PRL 109,…”

mentioning

confidence: 99%

“…Although an experimental observation is still lacking and all the evidence comes from extensive calculations, at least 11 neutral atoms are supposed to bind a positron in their ground state [12,13]. In contrast, very few computational studies have been performed on excited states, and this is unfortunate since the existence of excited states of positronic atoms could provide a path to the experimental observation of these systems, similarly to what happened with the recent experimental observation of the dipositronium molecule [14] exploiting the existence of an excited state.…”

mentioning

confidence: 99%

Positron Binding to Lithium Excited States

Bressanini

2012

Phys. Rev. Lett.

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In the last 15 years hundreds of papers have been devoted to the study of positron-atom or positron-molecule interaction. A large body of evidence has accumulated showing that many atoms in their ground state can bind a positron forming an electronically stable system. Studies on the possibility that a positron binds to an atomic excited state, however, are scarce. The first atom that was proved able to bind a positron in its ground state is lithium. Surprisingly, nothing is known on the possibility that a positron could bind to one of its excited states. In this Letter we study the positron attachment to the 1s(2)2p (2)P(o), 1s2s2p (2)P(o) and 2p(3) (4)S(o) excited states of the lithium atom. While the (2)P(o) state cannot bind a positron, and the (4)S(o) could at most form a metastable state, a positron can attach to the (4)P(o) state of lithium forming a bound state with a binding energy of about 0.003 hartree. This state can alternatively be considered an excited state of the system e(+)Li and it could be, in principle, exploited in an experiment to detect e(+)Li, whose existence has been predicted theoretically but has not yet been observed experimentally.

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“…The most accurate calculations were performed for eleven positron-atom systems involving Li, Na, Ag, Cu, Au, Be, Mg, Ca, Zn, Sr and Cd atoms [7][8][9][10][11][12][13][14][15][16][17][18]. Recent empirical fitted expression involving the polarizabilities (α), ionization potentials (I), and numbers of valence s electrons has also been based on the best calculations mentioned above [19]. A number of positron-atom bound states involving atoms with open d subshells were studied in our previous paper [20].…”

Section: Introductionmentioning

confidence: 99%

Identification of atoms that can bind positrons

2014

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Calculations of the positron binding energies to all atoms in the periodic table are presented and atoms where the positron-atom binding actually exists are identified. The results of these calculations and accurate calculations of other authors (which existed for several atoms only) are used to evaluate recommended values of the positron binding energies to the ground states of atoms. We also present the recommended energies of the positron excited bound levels and resonances (due to the binding of positron to excited states of atoms) which can not emit positronium and have relatively narrow widths. Such resonances in positron annihilation and scattering may be used to measure the positron binding energy.

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Binding-energy predictions of positrons and atoms

Cited by 26 publications

References 28 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Positron Binding to Lithium Excited States

Identification of atoms that can bind positrons

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