Energy levels and spectrum of neutral helium (4He I)

Abstract

A table of energy levels based on the most accurate observations now available is given for the neutral 4He atom. The wavelengths contained in a revised list of 4He I lines from 320 A to 21132 A are also based on the best measurements, over half of them having been calculated from the wavenumber separations of appropriate levels. Several previously disturbing features of the 4He term scheme are obviated by the revised level values. In a discussion of the experimental results for this spectrum some comparisons with theory are made.