X-ray photodesorption intensities divided by the photon flux (in A s photon⁻¹) at 560 eV of desorbing masses from mixed ¹³CO:CH₃CN and H₂O:CH₃CN ices, irradiated at 15 K. The attribution of the desorbing species to the mass channels is displayed for the m/z 41, 27, 16, and 15. For the other mass channels, this attribution depends on the ice composition. This is discussed in the text. The signals were obtained for a fluence < 2 × 10¹⁶ photons cm⁻² and are not corrected for any possible fragmentation of desorbing species in the ionization stage of our QMS. The striped rectangles displayed on the m/z 28 for the ¹³CO-mixed ices correspond to the contribution of desorbing ¹²C¹⁶O originating from the isotopic impurities in our ¹³CO gas sample, as estimated in the text.