ABSTRACT A MgLi dilute alloy (6% wt. Li) has been studied by x‐ray emission spectroscopy in the ultra‐soft x‐ray range, 40–60 eV. For this purpose, a high‐resolution reflection zone plate spectrometer, working as a variable line grating spectrometer, was used on an electron probe microanalyser. With the experimental conditions, current and acceleration voltage of the incident electron beam, geometry, CCD detection, the Mg L emission band is easily observed. The Fermi edge of this band shifts toward the low photon energies with the Li content. The Li K emission band is hardly detectable despite the non‐negligible lithium mass fraction in the alloy. This is explained by the reabsorption of the lithium emission by the magnesium atoms, the reabsorption effect being strong in the present geometrical conditions of the experiment.