On the use of fused silica etalons in the study of hyperfine structure

The paper discusses the advantages of fused silica etalons in hyperfine structure analysis of spectral lines. It is shown that the temperature effect on the patterns produced by such plates is negligible as compared with that on patterns from Lummer plates either of quartz or of glass. Long exposures in photographing the patterns are thus rendered possible. The re-examination by the authors of a few prominent lines of mercury using these etalons has revealed faint satellites not previously recorded. A microphotogram showing a new satellite at −0.154 Å. for HgI 5461 Å. is here reproduced