Fig. 1.
The effect of accumulated electron fluence on (a) the valence and (b) the oxygen co-ordination of iron in haemosiderin and ferritin mineral cores (HMC and FMC respectively) as measured by fitting reference spectra to Fe L2,3-ionisation EELS edges recorded in the STEM. (c) The change in valence with progressively increasing electron fluence as measured by taking Fe L3 to L2- ratios from the same spectra used for a and b, following the method of van Aken and Liebscher (2002). (d) The highest fluence haemosiderin Fe L2,3-ionisation EELS edge with the four fitting reference spectra shown underneath and their intensity scaled by the fitting coefficients such that when summed they produce the best fit to the mixed valence spectrum (inset is the residual after fitting).