Open AccessNote on vacuum grating spectroscopy
Author(s) -
John Cunningham McLennan
Publication year - 1920
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1920.0057
Subject(s) - spectrograph , helium , spectroscopy , opacity , hydrogen , grating , physics , spectral line , emission spectrum , ultra violet , optics , atomic physics , optoelectronics , astronomy , quantum mechanics
In the spectroscopy of the extreme ultra-violet region, it is necessary to work either with arcsin vacuo or with sparks in one or other of the gases hydrogen or helium. As all other gases are opaque to ultra-violet radiations of short wave-length, their use is precluded. With many of the elements, arcs are difficult to maintain in a vacuum, and consequently one is driven to the use of sparks in either one or other of the two gases mentioned. Lyman, in his brilliant researches, has shown us that, with hydrogen, it is possible to obtain spectra extending to about λ 900 Å. U. For radiations below this limit, it would appear, however, that hydrogen is more or less absorbing.. With helium, on the other hand, the evidence available goes to show that this gas is transparent to radiations having wave-lengths as short as λ 400 Å. U. or λ 500 Å. U., and possibly shorter still. It would appear, then, that in the spectroscopy of the extreme ultra-violet, the procedure to be followed, which would permit of the most rapid progress being made, would be, in so far as the emission spectra are concerned, to work with a vacuum grating spectrograph, and to use an atmosphere of helium.