Open AccessThe hydrogen band spectrum: new band systems in the violet
Author(s) -
O. W. Richardson
Publication year - 1927
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.1927.0108
Subject(s) - excited state , spectrum (functional analysis) , physics , atomic physics , quantum mechanics
The system of bands described in this paper includes much of the strength of the secondary hydrogen spectrum when this is excited by direct electron impact on the H2 molecule and there are no additional complications. I first observed it on a photograph of the spectrum of hydrogen at a pressure below 0·01 mm. of mercury, excited by a sharply limited electron, stream, which was kindly sent to me by Mr. P. M. S. Blackett. This photograph, which was taken by Mr. Blackett, had insufficient resolution and dispersion for the identification of the lines of the secondary spectrum. Up to the present I have not been able to get sufficient intensity at low pressures to obtain this spectrum with the purity shown on Mr. Blackett’s photograph and the requisite resolution; but by working at pressures of about 0·3 mm. I have, with the help of Mr. D. B. Deodhar, got some plates on the large quartz Littrow spectrograph at King’s College which show this spectrum sufficiently enhanced and the rest sufficiently reduced for the main features to be recognised with confidence. The present paper deals with but a portion of what I have been able to arrange provisionally in this spectrum, but it is a unit which seems to be complete in itself, except that I am only able to give the Q branches of the bands, whereas there are indications, still insufficiently explored, that P and R branches do exist. There are two band systems, the first very strongly developed. The nucleus (0→0 Q (1) line) of the first band is at λ 4633·95 (9) =v 21573·81. The Q branch of the 1→0 band is the series 20Q (m ) of Richardson and Tanaka. All the bands are degraded towards the violet,i. e ., in the opposite sense to those in the systems described in Structure, Parts IV and V. Each line of the bands is accompanied by a fainter component on the long-wave side of it. The intensity of the fainter line is usually about one-fourth of that of the stronger in terms of the numbers of the usual conventional scale of intensities, and the separation of the two lines is in the neighourhood of 4 wave-numbers. The final states of the present bands appear to be the same as the initial states of the Lyman bands in the far ultra-violet.