Humphreys and Mohler, in 1896-7, made an extended study of the effect of pressure upon the wave frequencies of the lines of the emission spectra of a larger number of the metallic elements. The source used was an enclosed electric arc about which the air pressure could be varied, the pressure being carried up to fourteen atmospheres. The results of their experiments indicate that all isolated lines shift toward the red end of the spectrum with increased pressure, the shift being proportioned to the wave length for lines of a given series, but the factor of proportionality being different for lines of different series.
Proceedings of the Iowa Academy of Science
©1906 Iowa Academy of Science, Inc.
Almy, Frank F.
"The Effects of Presssure upon Lines in the Spectrum of Iron,"
Proceedings of the Iowa Academy of Science, 13(1), 231-232.
Available at: https://scholarworks.uni.edu/pias/vol13/iss1/34