Binding energy of the metastableHe−ion

Abstract

This paper presents theoretical ab initio calculations and experimental measurements of the binding energy of the metastable ${\mathrm{He}}^{\mathrm{\ensuremath{-}}}$1s2s2p${\mathrm{}}^{4}$P ion. The calculated 77.518\ifmmode\pm\else\textpm\fi{}0.011 meV and the measured 77.516\ifmmode\pm\else\textpm\fi{}0.006 meV values for the binding energy are in excellent agreement and they represent a significant improvement in the accuracy compared to previous studies. The experimental technique is based on the determination of the \ensuremath{\epsilon}s-wave Wigner threshold associated with detachment to the 1s3s${\mathrm{}}^{3}$S state of the neutral He atom. The yield of the 1s3s${\mathrm{}}^{3}$S He level was monitored by applying resonant ionization spectroscopy.