BINDING-ENERGY OF THE METASTABLE HE- ION

This paper presents theoretical ab initio calculations and experimenta l measurements of the binding energy of the metastable He(-)1s2s2p P-4 ion. The calculated 77.518+/-0.011 meV and the measured 77.516+/-0.00 6 meV values for the binding energy are in excellent agreement and the y represent a significant improvement in the accuracy compared to prev ious studies. The experimental technique is based on the determination of the epsilon s-wave Wigner threshold associated with detachment to the 1s3s S-3 state of the neutral He atom. The yield of the 1s3s S-3 H e level was monitored by applying resonant ionization spectroscopy.