Absorption Spectrum of the Hydrogen Molecule

Abstract

WITH the continuous spectrum described by Lyman (Astrophysical Jour., 60, 1) as a background, and with hydrogen flowing through the receiver of the spectrograph, it was found possible to photograph the absorption spectrum of molecular hydrogen in the extreme ultra-violet. More than twenty absorption bands were observed between λλ1245 and 840. Most of the bands were clearly resolved and show the characteristic structure of the emission bands in the ultra-violet. The most striking feature of the spectrum is a progression of strong absorption bands beginning with 1105. At least twelve bands of this progression were easily recognised. This adds a new electronic level to the three already obtained (Dieke and Hopfield, Oakland Meeting of the American Physical Society, June 1926) from the hydrogen emission spectrum. A continuous absorption spectrum begins sharply at 840. This continuous absorption corresponds to the dissociation of the molecule into a normal and an excited atom. The long wave-length limit of the continuous absorption compares well with the theoretical value 14.4 volts. Complete details will be published later.