About the N-series x-ray lines in the electron excited spectra of heavy elements

The electron excited N-series lines N4N6 and N5N7 of the element 74W were studied using both energy dispersive (ED) and wavelength dispersive spectrometry. In ED spectra these lines appear as one unresolved peak N4,5N6,7 at approximately 217 eV. The net peak height of this N-series peak relative to that of the unresolved Mαa,β (M4,5N6,7) peak decreases rapidly with an increasing energy of the exciting electrons, E0. One of the reasons for this dependence is the much stronger absorption of the N-series lines. Their mass absorption coefficient (m.a.c.) in 74W was estimated to be approximately 17000 cm2 g-1. The observation of the N-series peak in the ED spectra of 70Yb and 92U leads to the assumption that, in principle, the N-series peak should be observable for all elements 70≤Z≤92. The lack of knowledge about the N-series peaks can lead to serious misidentifications. The danger of such misidentifications increases with decreasing E0. (author)