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![[Figure 4]](xt0008fig4mag.jpg)
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Figure 4
X-ray absorption spectra (a) and first derivatives (b) of different organic and inorganic reference materials. The spectra are normalized between 0 and an edge jump of 1 and shifted vertically for clarity. Diplodon shell (AS07LS0026) and aragonite crystal were measured in situ with an acquisition time of 3 s; the other materials were measured as powder pellets with an acquisition time of 1 s; beam size on the samples were 350 µm × 200 µm. Line a in (a) marks the position of the Mn Kα pre-edge peak and line b shows the white line of the Mn Kα edge of the shell spectrum (at 6552 eV). Line c marks the secondary peak after the white line at 6564 eV in the shell spectrum. The arrow in (a) points to a prominent peak at 6578 eV in the MnO2 spectrum. (c) Close-up of the pre-edge region for reference substances with different oxidation states of Mn [aragonite: Mn(II); Mn-porphine: Mn(III); Mn-dioxide: Mn(IV); potassium permanganate: Mn(VII)] compared with the shell spectrum. The intensity and position of the pre-edge peak in the Diplodon shell spectrum corresponds best to that of Mn(II), while the peak in the spectra of the other reference compounds is shifted to higher energies. |
![[Figure 4]](xt0008fig4.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
