An Intensity Problem in the Spectrum of Potassium

By using a hollow-cathode discharge as a light source variations in the relative intensities of the three lines of the transition 4p-3d in K I at 11 690 A, 11 769 A and 11 772 A have been investigated and explained as an effect of self-absorption. Ten new lines and two previously observed lines in the extraphotographic infrared region have been measured. Improved photographic measurements of 4p-3d and 4p-10s have also been made, and part of the term system has been recalculated.