Stacked individual spectra covering 13 and 14 u q⁻¹ from the channel A (○) and channel B (□) of the MCP, each of them represents the accumulated counts during 19.8 s at the maximum gain step. Top panel: stacked spectra in low resolution covering both ranges (mass-per-charge ratios are indicated by the long ticks on the upper axis, half-integer ones by the short ticks). Panels underneath are HR spectra at specific u q⁻¹ : 13 (middle) and 14 (bottom), corrected from the pixel shift (see Fig. A.1). A statistical vertical error bar of , where N stands for the number of counts, is superimposed to the counts for information. The colour coding is given by the colour bar in Fig. 1 and relies on the time of acquisition during the escort phase. The mass-per-charge ratios of expected ions from Table 1 are also indicated and given in Table C.1.