National Synchrotron Light Source Seminar

This talk deals with in-situ experiments that make use of Scanning Transmission X-ray Microscopy (STXM) and Resonant Inelastic X-ray Scattering. First, a brief introduction is given of x-ray absorption spectroscopy, including the multiplet interpretation of XAS spectral shapes. (The atomic multiplet, crystal field and charge transfer effects will in detail be explained in the afternoon course).

With the recent developments in nanoreactors, soft X-ray STXM experiments make it possible to follow metal L edges at 1 bar and 500 C, with a spatial resolution of 20 nm. This allows the in-situ spectroscopic study of a single nanoparticle (in action). Recent STXM results show the spatial distribution of the degree of reduction of iron-oxide nanoparticles. A comparison is made with electron microscopy and some future directions of spectromicroscopy of nanomaterials are given.

The second part of the talk deals with the role of Resonant Inelastic X-ray Scattering (RIXS) to unravel the nature of the states that are visible in the pre-edge region of the 3d metal K edges. Using the 1s2p RXES of LiCoO2 as example, the presence of a 1s4p dipole pre-edge next to the traditional 1s3d quadrupole pre-edge is explained. A recent development is the combination of hard x-ray RIXS with XMCD, allowing the possibility to measure magnetic properties under extreme conditions. Soft X-ray RIXS allows the detection of charge transfer and dd-excitations. Recent improvements in energy resolution allow the detection of spin-orbit and magnetic excitations. Potential new applications for in-situ nanoparticle research are indicated.