Many-body theory of positron binding in polyatomic molecules

• DOI: 10.48550/arxiv.2105.06959
• Publication Date: 2021-01-01
• Authors: Jaroslav Hofierka; B. Cunningham; C. M. Rawlins; Charles H. Patterson; D. G. Green
• Keywords: Positronium; Positron annihilation spectroscopy

Positrons bind to molecules leading vibrational excitation and spectacularly enhanced annihilation. Whilst positron binding energies have been measured via resonant annihilation spectra for $\sim$90 in the past two decades, an accurate \emph{ab initio} theoretical description has remained elusive. Of studied experimentally, calculations exist only 6, these, standard quantum chemistry approaches proved severely deficient, agreeing with experiment at best 25% accuracy polar molecules, failing predict nonpolar molecules. The mechanisms of are not understood. Here, we develop a many-body theory positron-molecule interactions uncover role strong correlations including polarization electron cloud, screening positron-electron Coulomb interaction by molecular electrons, crucially, unique non-perturbative process virtual-positronium formation (where temporarily tunnels positron): they dramatically enhance enable nonpolars. We also elucidate individual orbitals, highlighting importance electronic $π$ bonds. Overall, calculate agreement (to within 1% cases), formamide nucleobases. As well as supporting experiments positron-based spectroscopy, approach can be extended scattering $γ$ condensed matter, provide fundamental insight predictive capability required properly interpret materials science diagnostics, antimatter-based technologies (including traps, beams emission tomography), understand positrons galaxy.