The absorption spectrum of potassium vapour

Abstract

In connection with the investigation of the vacuum arc spectrum of potassium, which was undertaken mainly to improve the existing measures, it was found that the type of lamp used in that experiment was unsuitable for the production of the higher members of the series. Already Wood has shown that the principal series of sodium is much more complete in the absorption than in the emission spectrum, and has extended the series up to m = 57. Bevan repeated the experiments with the other alkali elements and was able to extend the principal series in each case very considerably. In view of the importance of obtaining accurate measures of these lines and a possible extension of the series, so that they may afford data which will help to throw some light on the question as to the nature of the formula giving series lines, it was thought desirable to repeat the experiment of Bevan with instruments of greater dispersion. The results which have been accomplished in the repetition of the work may be briefly summarised as follows:— (1) The number of members of the series has been raised from twenty-four to forty-two. (2) The first seven members of the series have now been resolved into their components as compared with five in previous investigations. (3) Besides the absorption of the lines of the principal series, new lines have been found to be absorbed at somewhat higher pressure which seem to have no correspondence with the known lines in the emission spectrum. (4) An important result of the experiments is the observation of the absorption of the two combination lines 1 s —2 d and 1 s —3 d , the first as a pair confirming the presence of a satellite to the lines of the diffuse series, and the second as an unresolved line.