Single-quantum annihilation of positrons with shell-bound atomic electrons

Palathingal, J.C.; Asoka‐Kumar, P.; Lynn, K. G.; Posada, Y.; Wu, Xueguang

doi:10.1103/physrevlett.67.3491

Cited by 13 publications

(13 citation statements)

References 13 publications

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“…For free atoms, radiation-less and single-photon decay are suppressed by energy and momentum conservation requirements. These annihilation modes have been observed for thermalized positrons in the presence of a nucleus [180,181] or via in-flight annihilation by energetic positrons [182,183]. In general, however, ground state singlet and triplet Ps atoms predominantly decay into two or three photons, respectively.…”

Section: Ps Annihilationmentioning

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: Ps Annihilationmentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

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“…To our knowledge, the only data available on differential cross section have been obtained by us in our exploratory work on lead [17]. The results of this earlier work are presented in Table IV along with the parallel data from the present study.…”

Section: Discussionmentioning

confidence: 75%

“…The first high-resolution study of the phenomenon to our knowledge was made only recently [17]. In this experiment, which was performed by the present authors and was confined to lead, monoenergetic positrons were derived from an accelerator, with energy varying between 1 and 2 MeV.…”

Section: Theoretical Reviewmentioning

confidence: 99%

Nuclear-charge and positron-energy dependence of the single-quantum annihilation of positrons

Palathingal¹,

Asoka‐Kumar²,

Lynn³

et al. 1995

Phys. Rev. A

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We report an experimental study of the single-quantum annihilation of positrons in a number of elements having atomic numbers between 49 and 90, utilizing a monoenergetic positron beam. Measurements were made of the differential cross sections for the forward direction for the I(, L, and M atomic shells in targets of Th, Pb, Au, Hf, Gd, and In, having thicknesses that vary between 2.7 and 4.4 mg/cm . A shielded HPGe detector of high relative photopeak eKciency was used for recording the photon spectrum. Values for the individual atomic shells were obtained in the positron kinetic-energy range 1. 02 -2.24 MeV. It was observed that the differential cross sections measured for the forward direction varied with energy for each major shell almost alike so that the shell ratios appeared to remain constant while the positron energy varied. The dependence of the cross section on the atomic number Z of the target element was tested for each of the major shells at various energies of measurement. It was seen that the cross sections follow a Z' relation with v= 5. 1 as the exponent for the K shell. For the higher shells, the exponent is approximately 6.4, which is significantly larger. It was also noted that this pattern is fairly independent of the positron energy. The results on the Z dependence are seen to be clearly at variance with the most updated theoretical predictions.PACS number(s): 34.90.+ q, 78.70.8j

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“…One γ -ray annihilation is forbidden by the conservation of energy and momentum when there is no third body to receive the residual momentum. (When such a body is present, not only one γ -ray annihilation [6,7] but also radiationless annihilation can occur [8].) Therefore most positrons annihilate with the electrons which make singlet pairs with the positrons and annihilate into two γ -rays in matter.…”

Section: Positronsmentioning

confidence: 98%

Experiments on positronium negative ions

Nagashima

2014

Physics Reports

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Single-quantum annihilation of positrons with shell-bound atomic electrons

Cited by 13 publications

References 13 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Nuclear-charge and positron-energy dependence of the single-quantum annihilation of positrons

Experiments on positronium negative ions

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