Relative Excitation of the Three X-ray L-Levels with Cathode Rays of Different Velocities

Abstract

SKINNER, Robinson, and others have studied the relative excitation of the three X-ray levels L_III, L_II, and L_I, when for this excitation primary radiation of different wave-length is used. Such experiments may be done by studying the relative intensity of the emission lines which combine with each of the three L-levels (Skinner) or by an estimation of the relative intensity of the secondary β-rays which emerge from these levels (Robinson). The following remarkable result was obtained : when the exciting radiation is a little harder than that of the hardest L-absorption edge (L_I-), then the levels L_III and L_II give much more intense lines than the level L_I. With increasing frequency, however, this relation is totally changed in favour of L_I. With a frequency about five times as large as that of the L-edges, L_I is excited to a much larger extent than L_II and L_III, so that the generally not very intense lines belonging to L_I become the most intense lines of the corpuscular β-ray spectrum in the experiments such as done by Robinson. This result points to the large influence of the quantum number l (which is 1 for L_III and L_II and 0 for L_I) on the excitation of the three L-sublevels.