Improved lower bounds to energy levels (of 1s ns1S states of He)

Abstract

Improved lower bounds to the energy levels of the 1s ns 1S states of helium through n=6 have been calculated with analytical orbital wavefunctions using an extension of the methods of Cohen and Feldmann (see abstr. A51946 of 1970). For the excited states, these bounds are all within 1.25% of the observed levels, and the error reduces to 0.15% for the highest levels. These results confirm the reliability of the frozen core wavefunctions for excited states.