Electron Energy Loss Spectroscopy and Near Edge Fine Structure Analysis

When fast electrons (50kV-1MV) pass through a transmission electron microscope specimen they can loose energy by exciting electrons associated with atoms in the spectrum. The distribution of transmitted electrons as a function of energy loss is called an energy loss spectrum. There are sharp increases in intensity known as an inner shell edges when the energy loss is equal to the binding energy of an inner shell electron. These features can be used for microanalysis, and in my earlier work I used various atomic physics (Hartree-Fock-Slater, Dirac-Fock) programs to calculate appropriate ionisation cross sections. I am now more interested in understanding the near edge structure and using it to give information about bonding, coordination and charge transfer on an atomic scale. I have been applying various approaches based on modern electronic structure techniques (Full Potential Linearised Augmented Plane Wave (FLAPW), Layer Korringa Kohn Rostoker (LKKR), Pseudopotential) to the calculation of the densities of unoccupied states and the resulting near edge fine structures.

Past Graduate Students Involved in This Work: X Weng, J. Auerhammer, J. Alvarez
 

   LKKR calculation for O K edge in TiO2Solid line calculation, dashed line experiment

               Pseudopotential calculation for C K edge in diamond, solid line experiment.

Some representative publications

  • "K, L and M Shell Generalised Oscillator Strengths and Ionisation Cross Sections" R.D. Leapman, P. Rez and D.F. Mayers, J. Chem. Phys.,1980, 72, 1232-1243.
  • "Electron Ionisation Cross Sections for K, L and M Shells" P. Rez, X-ray Spectrometry, 13, 1984, 55-59.
  • "Inner Shell Edge Shapes in Electron Energy Loss Spectroscopy" C. Ahn and P. Rez, Ultramicroscopy, 17, 1985, 105-115.
  • "Pseudo Atomic-Orbital Band Theory Applied to Electron Energy Loss Near Edge Structures", X. Weng, P. Rez and O.F. Sankey, Phys. Rev., B40, 1989, 5694-5704.
  • "Review of methods for calculating near edge structure", P. Rez, J. Bruley, P. Brohan, M.C. Payne and L.AJ. Garvie, Ultramicr.,59, 1995, 159-167.
  • "Application of the Layer Korringa Kohn Rostoker Method to the Calculation of Near Edge Structure in X-ray Absorption and Electron Energy Loss Spectroscopy", P. Rez, J. M. Maclaren and D.K. Saldin, Phys. Rev. B57 , 1998, 2620-2627.