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X-ray Spectroscopy

 

We investigate the dynamics of charges in and the structures of complex molecules. The spatial resolution in x-ray spectroscopy originates in the transition that involve strongly bound core electrons as initial and/or final states.

 

In x-ray absorption spectroscopy (XAS) the energy of the absorbed photon raises an electron from a deeply bound state into unoccupied bound states or or gains enough energy to escape the complex. The absorption spectrum thus contains detailed information about the density of empty states and allows conclusions about coordination, oxidation state and many more of the local structure. (processes A and B) While there are a number of names framed for this type spectroscopy x-ray absorption near edge spectroscopy (XANES) is commonly understood. If the energy of the the photon is sufficient to overcome the binding potential the electron the absorption probability is influence by a electron scattering process from the local environment of the absorbing atom. This technique is often call EXAFS and can be used to refine the local structure around the absorbing atoms.

XAS is the least photon hungry of the spectroscopies we are using. It requires either the selection or dispersion of the exciting/absorbed beam. It is particulary useful if the absorbing atom is uniquely placed in the complex. 

Page in work:

Other techniques we are using are 

X-ray emission spectroscopy (XES)
X-ray Photoelectron spectroscopy (XPS)
and x-ray diffuse scattering (XDS)

We are also developing novel approaches to table-top spectroscopy using novel very efficient energy dispersive detection technology

 

 

Element selective spectroscopy can probe the local charge distribution. The involvement of highly localized electronic orbitals in the observed transitions is creating an "atomic sensor" in a complex molecular environment.