Effect of 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 $2s2p{}^3{P}_2^o$ 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.

arXiv comment5 pages, 1 figure

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