X-ray inverse fluorescence approach for accurate determination of Fe valence in Fe-rich geological materials

Nakada, Ryoichi*; Okuda, Hanaya*; Suga, Hiroki*; Yamaguchi, Akiko  ; Takahashi, Yoshio*; Kawazoe, Takaaki*

Iron undergoes redox transitions between ferrous (Fe) and ferric (Fe) states, playing a key role in various geoscientific processes from Earth's interior to surface environments. Partial fluorescence yield X-ray absorption near edge structure analysis (PFY-XANES) is widely used to evaluate iron valence, but it is susceptible to thickness and self-absorption effects in high-concentration samples. In this study, we applied the inverse fluorescence yield method (IPFY) to geological samples and demonstrated that it enables more accurate iron valence determination than PFY. IPFY-XANES suppressed overestimation of the Fe ratio and reduced thickness effects. This method is expected to be a powerful non-destructive tool for analyzing natural samples such as meteorites and high-pressure recovered specimens.