The M emission spectrum of 68 Er 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 M 5 O 3 line from the neighboring a M 5 N 7 transition. In addition to the five lines/bands tabulated in the classical paper of Bearden, a number of further lines were observed. These are . For all the lines with an energy below the M

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... absorption structure~M 5 O 3 , M 3 N 1 , M 4 N 3 , and z M 5 N 3 !, an increasing relative intensity with increasing energy of the exciting electrons, E 0 , was observed. This dependence has its origin in the fact that these lines are normally absorbed whereas Ma~M 5 N 7 ! and Mb~M 4 N 6 ! are additionally affected by anomalous line-type absorption.