Polaron-formation revealed by transient XUV imaginary refractive index changes in different iron compounds.

We use transient extreme ultraviolet (XUV) reflection absorption spectroscopy to study polaron formation on hematite and akaganeite surfaces. We observed a reduction in the offset of the imaginary refractive index (κoffset) that was attributed to the photoemission cross-section. The difference in the κoffset reduction indicated that deeper-trapped polarons were formed in hematite than in akaganeite.