The M Emission Spectrum of⁶⁸Erbium

The M emission spectrum of⁶⁸Er was reinvestigated using wavelength dispersive spectrometry, with a TAP diffracting crystal. By recording the spectra using the second-order reflection, an improved energy resolution was achieved, which is necessary to resolve the M₅O₃line from the neighboring α M₅N₇transition. In addition to the five lines/bands tabulated in the classical paper of Bearden, a number of further lines were observed. These are M₁N₃, M₃O₁, M₂N₁, M₅O₃, M₃N₁, and M₄N₃. For all the lines with an energy below the M₅absorption structure (M₅O₃, M₃N₁, M₄N₃, and ζ M₅N₃), an increasing relative intensity with increasing energy of the exciting electrons,E₀, was observed. This dependence has its origin in the fact that these lines are normally absorbed whereas Mα (M₅N₇) and Mβ (M₄N₆) are additionally affected by anomalous line-type absorption.