Abstract
LONDON. Royal Society, June 19.—Sir J. J. Thomson, president, in the chair.—The Hon. R. J. Strutt: Bakertian lecture: A study of the line-spectrum of sodium as excited by fluorescence. An improved form of sodium, vapour lamp, in quartz, was described, giving an intensely bright sodium spectrum, admirably adapted, for exciting sodium vapour to resonance. It is found that excitation of sodium vapour by the second line of the principal series leads to the emission of both λ 3303 and the D line. On the other hand, as might be expected, excitation by the D line leads to the emission of the D line only, without 3303. If only one of the components of the doublet 3303 is stimulated, both-the D lines are emitted. When D light falls on sodium vapour of appropriate density, it is known that an intense surface emission occurs from the front layer, and a weaker one from succeeding layers. Analysis by absorption in an independent layer of sodium vapour shows that the superficial emission is more absorbable, and therefore nearer the centre of the D lines. The breadth of the D lines in superficial resonance has been estimated by interferometer methods. It is found to correspond with the breadth conditioned by the Doppler effect, calculated on the assumption that the luminous centre is the sodium atom. Polarisation could not be detected in the ultraviolet resonance radiation, though, in accordance with previous observers, it was readily observed in D resonance.
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Societies and Academies . Nature 103, 359–360 (1919). https://doi.org/10.1038/103359a0
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DOI: https://doi.org/10.1038/103359a0