Related papers: Positron annihilation and binding in aromatic and …
We present first-principles approaches based on density functional theory for calculating positron states and annihilation characteristics in condensed matter. The treatment of the electron-positron correlation effects (the enhancement of…
In the annihilation of a positron with a bound atomic electron, the virtual gamma photon created may excite the atomic nucleus. We put forward this effect as a spectroscopic tool for an energy-selective excitation of nuclear transitions.…
The two-photon positron annihilation density matrix is found to separate into a diagonal center of energy factor implying maximally entangled momenta, and a relative factor describing decay. For unknown positron injection time, the…
In this paper we use a zero-range potential (ZRP) method to model positron interaction with molecules. This allows us to investigate the effect of molecular vibrations on positron-molecule annihilation using the van der Waals dimer Kr2 as…
Studies based on imaging the annihilation of the electron (e$^{-}$) and its antiparticle positron (e$^{+}$) open up several interesting applications in nuclear medicine and fundamental research. The annihilation process involves both the…
Topological insulators are attracting considerable interest due to their potential for technological applications and as platforms for exploring wide-ranging fundamental science questions. In order to exploit, fine-tune, control and…
We approach to the ortho-positronium (o-Ps) as a relativistic two-body problem in $2+1$ dimensions in which o-Ps is composed of two-oppositely charged particles interacting via an attractive Coulomb force. In addition to separation of…
Here we describe an advanced multi functional, variable-energy positron beam system capable of measuring the energies of multiple positron-induced electrons in coincidence with the Doppler-shifted gamma photon resulting from the…
Positron physics touches on a wide-ranging variety of fields from materials science to medical imaging to high energy physics. In this paper we present the development of a flexible positron annihilation spectrometer appropriate for the…
The emission spectra of many pi-conjugated polymers and oligomers contain side-band replicas with apparent frequencies that do not match the Raman active mode frequencies. Using a time dependent model we show that in such many mode systems,…
A long-standing problem to account for the electron-positron annihilation in positron Hydrogen scattering above the Positronium formation threshold has been resolved by the use of the three-body Faddeev formalism. The multichannel…
Measurements of the two dimensional angular correlation of the electron-positron annihilation radiation have been done in the past to detect the momentum spin density and the Fermi surface. We point out that the momentum spin density and…
A new relativistic method for calculation of positron binding to atoms is presented. The method combines a configuration interaction treatment of the valence electron and the positron with a many-body perturbation theory description of…
Measuring the Doppler broadening of the positron annihilation radiation or the angular correlation between the two annihilation gamma quanta reflects the momentum distribution of electrons seen by positrons in the material.Vacancy-type…
Recently it has been proposed that the positron, the anti-particle analog of the electron, is capable of forming an anti-matter bond in a composite system of two hydride anions and a positron [Angew. Chem. Int. Ed. 57, 8859 (2018)]. In…
Three-photon annihilation of the electron-positron pairs (= $(e^{-}, e^{+})-$pairs) is considered in the electron rest frame. The energy of the incident positron can be arbitrary. The analytical expression for the cross-section of…
Rates of the two-, three-, four- and five-photon annihilations of the electron-positron pairs are determined numerically for the three-body positronium ion Ps$^-$ ($e^- e^+ e^-$) and four-body bi-positronium `molecule' Ps$_2$ ($e^- e^+ e^-…
Positron binding energies in the negative ions H$^-$, F$^-$, Cl$^-$ and Br$^-$, and the closed-shell atoms Be, Mg, Zn and Ca, are calculated via a many-body theory approach developed by the authors [J.~Hofierka \emph{et al.} Nature~{\bf…
The annihilation parameters of positrons with electrons in different shells of Argon, Iron and Copper atoms are calculated below the positronium (Ps) formation thresholds. Quite accurate ab initio calculations of the bound state…
The explicit expression for the R-ratio of electron-positron annihilation into hadrons, which properly accounts for all the effects due to continuation of the spacelike perturbative results into the timelike domain, is obtained at an…