Related papers: Calculations of positron binding and annihilation …
A model-potential approach has been developed to study positron interactions with molecules. Binding energies and annihilation rates are calculated for positron bound states with a range of alkane molecules, including rings and isomers. The…
A model-potential method is employed to calculate binding, elastic scattering, and annihilation of positrons for a number of atoms and small nonpolar molecules, namely, Be, Mg, He, Ar, H$_2$, N$_2$, Cl$_2$, and CH$_4$. The model potential…
Enhanced positron annihilation on polyatomic molecules is a long-standing and complex problem. We report the results of calculations of resonant positron annihilation on methyl halides. A free parameter of our theory is the positron binding…
The model-potential approach previously developed by the authors to study positron interactions with molecules is used to calculate the positron binding energy for $n$-alkanes (C$_n$H$_{2n+2}$) and the corresponding cycloalkanes…
The aim of this work is to identify the mechanisms responsible for very large rates and other peculiarities observed in low-energy positron annihilation on molecules. The two mechanisms considered are: (i) Direct annihilation of the…
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…
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…
Positrons bind to molecules leading to vibrational excitation and spectacularly enhanced annihilation. Whilst positron binding energies have been measured via resonant annihilation spectra for $\sim$90 molecules in the past two decades, an…
Measured and calculated positron binding energies are presented for a range of hydrocarbons with up to six carbon atoms (viz., methane, acetylene, ethylene, ethane, propane, butane, and hexane) and their chlorinated counterparts. Both…
Annihilation spectra are presented for aromatic and heterocyclic ring molecules resolved as a function of incident positron energy using a trap-based positron beam. Comparisons with the vibrational mode spectra yield positron-molecule…
We present the positron coupled cluster singles and doubles (POS-CCSD) method to calculate positron binding energies in molecules. This framework treats electrons and positrons on an equal footing and includes up to simultaneous…
A many-body theory approach developed by the authors [Phys. Rev. A 70, 032720 (2004)] is applied to positron bound states and annihilation rates in atomic systems. Within the formalism, full account of virtual positronium (Ps) formation is…
Positron binding energies in halogenated hydrocarbons are calculated \emph{ab initio} using many-body theory. For chlorinated molecules, including planars for which the interaction is highly anisotropic, very good to excellent agreement…
The recently developed ab initio many-body theory of positron molecule binding [J. Hofierka et al., Nature, 606, 688 (2022)] is combined with the shifted pseudostates method [A. R. Swann and G. F. Gribakin, Phys. Rev. A 101, 022702 (2020)]…
A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to…
A method is proposed for detecting positron-atom bound states by observing enhanced positron annihilation due to electronic Feshbach resonances at electron-volt energies. The method is applicable to a range of open-shell transition metal…
Positron scattering and annihilation on noble gas atoms below the positronium formation threshold is studied ab initio using many-body theory methods. The many-body theory provides a near-complete understanding of the…
Positron binding in parabenzoquinone is studied using \textit{ab initio} many-body theory. The effects of electron-positron correlations including polarization, virtual positronium formation and positron-hole repulsion, as well as those of…
Diagrammatic many-body theory is used to calculate the scattering phase shifts, normalized annihilation rates $Z_{\rm eff}$ and annihilation gamma spectra for positron collisions with the hydrogen-like ions He$^+$, Li$^{2+}$, B$^{4+}$ and…
Doppler-broadened $\gamma$-ray spectra for positron annihilation on molecules are calculated using many-body theory. By employing Gaussian bases for the electron and positron wavefunctions, a computable expression that involves a…