Normalized desorption behaviour of N₂ and ¹³CO as a function of temperature in the ices. Please note that not all measured data is displayed. A figure showing the complete data is shown in Appendix D. Left: evolution of N₂, calculated from the m/z = 14 signal, during the TPD of different ices as a function of the temperature. The data have been sorted with respect to the N₂ present in the ice mixture. The shaded regions correspond to the desorption regions in Table 2. A lighter line color corresponds to more N₂. The linestyles indicate the amount of CO₂ present with respect to water, with the assignment being: x < 1%:dashed, 1 < x < 5%: long dashes, 5 < x < 10%:solid, 10 < x < 15%: dashdot, 15 < x < 20%: dashdotdotted, 20 < x%: dotted. Right: evolution of ¹³CO, calculated from the m/z = 29 signal, as a function of the temperature. The data have been sorted with respect to the ¹³CO present in the ice mixture. A lighter color corresponds to more ¹³CO. The linestyles indicate the amount of CO₂ present with respect to water, with the assignment of the linestyles being the same as for the left panel.