New Regularities in the Band Spectrum of Helium

Abstract

THE letter (NATURE, May 19) of Messrs. Takamine, Dieke, and Suga, reporting certain results in connexion with the analysis of the band spectrum of helium, was of peculiar interest to me, in view of the fact that I was proposing shortly to incorporate many of them in Part V. of a series of papers dealing with this subject. Mr. A. Harvey, working in collaboration with me, has measured and interpreted a number of new bands, chiefly in the less refrangible region, and, so far as can be gathered from the letter in question, has arrived at substantially similar conclusions. There appears to be at least one important difference of interpretation, but discussion of this had better await detailed publication. Meanwhile it may avoid confusion to remark that in all probability the band 3X → 2P (‘ortho-He’) of Takamine, Dieke, and Suga, is that near λ5885 already described in Part IV. (Proc. Roy. Soc, A, 118, p. 157), whilst one designated 4Z→2P by Dr. Jevons and myself in a paper at present awaiting publication is actually the next series member to their 3Z→2P. It is remarkable, and fortunate, that the same symbols X and Z have been respectively chosen in both cases for the new levels. The latter was employed in our case because of the large and unusual Zeeman effect exhibited by the lines of this band.