Many-body theory of positron binding to polyatomic molecules

Abstract

Positron binding to molecules is key to extremely enhanced positron annihilation and positron-based molecular spectroscopy1. Although positron binding energies have been measured for about 90 polyatomic molecules1–6, an accurate ab initio theoretical description of positron–molecule binding has remained elusive. Of the molecules studied experimentally, ab initio calculations exist for only six; these calculations agree with experiments on polar molecules to at best 25 per cent accuracy and fail to predict binding in nonpolar molecules. The theoretical challenge stems from the need to accurately describe the strong many-body correlations including polarization of the electron cloud, screening of the electron–positron Coulomb interaction and the unique process of virtual-positronium formation (in which a molecular electron temporarily tunnels to the positron)1. Here we develop a many-body theory of positron–molecule interactions that achieves excellent agreement with experiment (to within 1 per cent in cases) and predicts binding in formamide and nucleobases. Our framework quantitatively captures the role of many-body correlations and shows their crucial effect on enhancing binding in polar molecules, enabling binding in nonpolar molecules, and increasing annihilation rates by 2 to 3 orders of magnitude. Our many-body approach can be extended to positron scattering and annihilation γ-ray spectra in molecules and condensed matter, to provide the fundamental insight and predictive capability required to improve materials science diagnostics7,8, develop antimatter-based technologies (including positron traps, beams and positron emission tomography)8–10, and understand positrons in the Galaxy11.

Maxwellianization of Positrons Cooling in CF4 and N2 Gases

“…We consider only fundamental transitions, and, initially, we consider only the dipole-active modes and neglect positron-positron collisions. The true positron-molecule interaction is characterized by strong positron-molecule correlations; whilst ab initio many-body theory has recently enabled calculations of binding and elastic scattering on ground-state molecules [51,52], the accurate ab initio calculation of inelastic cross sections remains a formidable and open problem. To proceed, we make use of the Born-dipole cross sections σ 0⇄3;4 for transitions between the ground state and dipole-active modes ν 3 and ν 4 [32,39,53].…”

“…Positron-molecule correlations may modify the inelastic cross sections and rotational dynamics. However, ab initio calculation of positron-molecule inelastic scattering cross sections is a challenging, long-standing open problem (our recently developed positron-molecule many-body theory [51] may be extended to calculate ab initio inelastic FIG. 3.…”

Viewpoints on the 11th International Meeting on Atomic and Molecular Physics and Chemistry

“…The process significantly enhances binding in organic polar molecules which is essential to support binding in nonpolar molecules including CS 2 , CSe 2 , and benzene. 12 The contribution of Jaroslav Hofierka was selected as one of the three Best Hot Topic contributions of the conference. The hot topic by Eva Klimesǒváreported a study of CsCl nanoparticles (with diameters of a few 100 nm) in a helium atmosphere interacting with intense NIR and XUV lasers.…”

“…The theory taking ab initio account of the correlations was applied to better describe virtual-positronium formation. The process significantly enhances binding in organic polar molecules which is essential to support binding in nonpolar molecules including CS 2 , CSe 2 , and benzene . The contribution of Jaroslav Hofierka was selected as one of the three Best Hot Topic contributions of the conference.…”

Rearrangement Collisions in the Schwinger Variational Principle: A Long-Standing Problem in Positron Scattering Physics

“…It is well known that the virtual Ps formation effect is one of the main ingredients for a good Z eff calculation 12−14 and is also essential to correctly describe the positron binding to polyatomic molecules. 15 Thus, one may wonder: how can the virtual/real Ps formation be properly accounted for in the SVP?…”