Intensity Measurements in the Spectrum of Manganese

Relative intensity measurements have been made for the lines of twenty-five multiplets of manganese, containing about one hundred and fifty lines in all. All but three of these were of Mn I. None of the Mn II multiplets measured were found to contain lines of abnormal intensity. On the other hand, at least eight multiplets of Mn I contain lines which are clearly anomalous. These eight multiplets contain a large number of the strongest lines of the spectrum. All involve terms derived from the term a⁵D of Mn II and are of the inverted type with wide separations between the sub-terms. There seems to be regularity in the departure from normal intensities which can best be described by graphs in which the calculated intensities are plotted against the measured intensities on double logarithmic paper. In these plots, the satellites often assume a regular pattern above or below the main diagonal lines.The total relative intensities of seventeen of these multiplets have also been measured. After reasonable excitation corrections have been applied, the agreement of their intensities with the theoretical values is as close as is to be expected. The measurements on the quartet triad of this group are the most reliable.