On the spectrum of neutral helium

Abstract

Silberstein's formula for the lines of neutral helium.- As objections to the validity of the formula ν=4N (I/n₁²-I/m₁²+I/n₂²-I/m₂²) it is pointed out that the ionizing potential computed by means of this formula does not agnee with that given by experiments; that no definite principle of selection has been given to indicate observable lines; that there is no arrangement of lines as regards series relationship, division into singlet and doublet systems, or of intensities. The difference between the actual and the calculated frequencies is shown to be the same as that to be expected on the assumption that the coincidences are purely accidental; and the same frequencies can be obtained with different sets of numbers.