Core Level Spectroscopy
Creation and Decay of Core Holes
Spectroscopic Techniques

Introduction

Core level spectroscopy pro vides a method to study the chemical state, local geometric structure, nature of chemical bonding, and dynamics in electron transfer processes centered around one atomic site via the mechanisms of x-ray induced core hole creation and decay.

The ejection of a core electron is initiated by the absorption of an x-ray photon (produced by synchrotron radiation) with energy tuned to the electron's ionization as shown here.

Core-holes are created by core-level ionization
and x-ray absorption processes.|

The core-hole decays by radiant and non-radiant processes.

The resulting excitations and relaxations form
the basis for the various core level x-ray spectroscopies.
How?
An example, please...




How is the ejection of a photoelectron related to the different spectroscopic techniques?



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The different spectroscopic techn iques can
be separated into two classes, corresponding
to the creation and decay of core-holes.

The creation of core holes forms the basis for:

X-ray Photoelectron Spectroscopy (XPS)
X-ray Absorption Spectroscopy (XAS)

The subsequent core hole decay is studied in:

Auger Electron Spectroscopy (AES)
X-ray Emission Spectroscopy (XES)


How can we use these techniques to gain important information about model systems?



Here's an example...

To the right is an illustration of the
local probing character of core
level spectroscopies applied to N2 adsorbed on Ni(100).

The grey area represents the charge density outside the metal surface
with a cut into the molecular adsorbate. Electronic transitions between core
and valence ele ctrons are indicated
with arrows.

Click here to see the XPS, XAS, XES,
and AES spectra for this system.


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