Specific Coster–Kronig (CK) transitions in 3d
transition
metals are close to the threshold of energetic possibility, being
disallowed in free atoms, while possible in solids. Moreover, they
have been shown to be quite sensitive to chemical bonding. Nevertheless,
there has been no direct study of such behavior in solution. Here
we present an approach to quantify such transitions in solution, by
comparing relative fluorescence of different edges to their relative
absorption strengths. The difficulties of acquiring a measurement
of the absorption in solution are overcome by applying the recently
developed method of inverse partial fluorescence yield to a liquid
sample using the microjet. This method has been demonstrated on solids
to be bulk sensitive and able to obtain absorption spectra free of
self-absorption or saturation effects. We extend this approach to
investigate the L-edge of aqueous Fe2+ using a combination
of a soft X-ray light source and a high-resolution X-ray emission
spectrometer.