Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules, using a Gaussian basis

Abstract

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 contains one free parameter for each type of atom within the target. Its values are chosen to reproduce existing ab initio positron-atom binding energies or scattering phase shifts. The calculations are performed using a Gaussian basis for the positron states, and we show how to obtain values of the scattering phase shifts and normalized annihilation rate $Z_{\mathrm{eff}}$ from discrete positive-energy pseudostates. Good agreement between the present results and existing calculations and experimental data, where available, is obtained, including the $Z_{\mathrm{eff}}$ value for CH${}_4$, which is strongly enhanced by a low-lying virtual positron state. An exception is the room-temperature value of $Z_{\mathrm{eff}}$ for Cl${}_2$, for which the present value is much smaller than the experimental value obtained over 50 years ago. Our calculations predict that among the molecular targets studied, only Cl${}_2$ might support a bound state for the positron, with a binding energy of a few meV.

arXiv comment23 pages, 10 figures, accepted in Phys. Rev. A

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Cited by in corpus (6)

• Effect of chlorination on positron binding to hydrocarbons: experiment and theory
• Effect of molecular constitution and conformation on positron binding and annihilation in alkanes
• Many-Body Theory Calculations of Positron Scattering and Annihilation in H${}_2$, N${}_2$ and CH${}_4$
• Many-body Theory Calculations of Positron Binding to Halogenated Hydrocarbons
• Positron cooling via inelastic collisions in CF${}_4$ and N${}_2$ gases
• Two-photon Annihilation of Positrons with K-shell Electrons of H-like ions