This figure shows the correction (described in Sect. 2.3) applied to all N₂ data (grey, dash-dotted). The m/z = 28 signal consists out of contributions from both N₂ and CO₂, which necessitates the correction. Furthermore, a simple data correction has been performed, namely only summing the m/z = 28 and m/z = 14 signal and correcting for the expected fractionation pattern (red, dashed), which gives very similar results in the region where the only contribution to m/z = 28 is N₂.