TEY from ammonia ices over different fluence ranges, at 23 (a) and 75 K (b). The inlets in panels a and b show the TEY below 400 eV. Panel c shows a zoom-in of the ammonia TEY around 401 eV (at 75 K) compared to the partial electron yield (PEY) from a pure N₂ ice from Feulner et al. (1992), in arbitrary units. N₂ formation during irradiation of ammonia ices is confirmed by the appearance of the N₂ vibronic structure (green trace, spectral resolution of 20 meV). The legend gives the initial and final fluences for each energy scan. The photon flux is ~2 × 10¹¹ ph s⁻¹ for the black and green traces and ~2 × 10¹² ph s⁻¹ for the others.