Effect of the atomic electric quadrupole moment on positron binding

Abstract

Effect of the electric quadrupole moment, Q, is studied for positron-atom bound systems. It is demonstrated that for Q > 50 a.u. the electric quadrupole potential is sufficiently strong to bind positron (or electron) even in the absence of the dipole polarization potential. Such large values of Q are not known for atomic ground states, however, they exist in molecules and excited atoms. In the state 2s2p 3 P o 2 of beryllium, the quadrupole contribution makes difference between stable bound state and decay to Be + ion and positronium. In a majority of atoms the quadrupole contribution is small and can be neglected.

Electron superhalogens as positronium superhalogens

“…Analyses of the binding of positrons to neutral atoms and molecules have revealed direct correlations of positron affinities with the polarizabilities, dipole moments, and quadrupole moments of isolated species. [15][16][17][18][19][20] The binding energy of a positron to a neutral molecule typically falls below 1 eV and generally has minimal impact on the electronic structure and geometry of the host system. 7 Positrons can also bind to anionic systems, with binding energies often exceeding 1 eV.…”

Low Energy Positron Scattering by F and F2

“…Even though the quadrupole value of this atom is small when compared to molecules, it is sufficient to make the scattering potential spherically anisotropic. According to Harabati et al, the quadrupole moment of the F atom is insufficient to generate a bound state, nevertheless the effect of this atomic quadrupole on the scattering cross sections is worth being investigated.…”