Spectroscopy core hole excited states

AES Auger Electron Spectroscopy Core-hole excitations are created, usually by 1-10 KeV incident electrons, and Auger electrons of characteristic energies are emitted through a two-electron process as excited atoms decay to their ground state. AES gives information on the nearsurface chemical composition. 

The core loss structure in electron energy loss spectroscopy (EELS) is known to be very similar to XANES, because the core loss spectrum is caused by physically the same process as that of x-ray absorption, corresponding to the electronic transition from core level to unoccupied excited states. Therefore, the theoretical analysis for ELNES can be carried out by almost the same procedure used for that of XANES. For the chemical state analysis of oxide ceramics, ELNES has also been proved to be very efficient with theoretical analysis by DV-Xa cluster calculation . The cluster calculation indicates that the core-hole effect due to the electronic transition is sometimes very important and the ground state calculation gives a serious errors in excited electronic state. 

X-ray absorption near edge structure(XANES) and electron energy loss near edge structure(ELNES) show similar spectra, thus almost the same theoretical analysis is valid both for these spectroscopies. The careful analysis including higher excited atomic orbitals in the basis set reproduce very well the spectral structure even in details. The core-hole effects are sometimes very important in the excited state electronic state. The theoretical analysis by the cluster model calculation provides very useful information on the local electronic property and the micro structure. 

The Auger effect is an important process in solid state spectroscopy. One can use resonant Auger spectra to study the nature of core excitation in ionic solids by examining the Auger structure, the nature of the core holes can be determined, as well as the splitting of the states by the ligand field. 

The final example in this set is the pair of elements Ge and Sn [352], for which the outermost d subshell absorption spectra lie above the doubleionisation limit. As a result of Auger broadening of the parent ion core, very few Rydberg members are observed. As already noted in section 6.8, series become rather short when the parent ion state (the core hole) which serves as the series limit is broadened by Auger processes. The resonances arising by inner-shell excitation become very diffuse, and little can be done by way of detailed spectroscopy except to observe the leading series members. 

In atoms and molecules, shakeup satellites, corresponding to internal electronic transitions, are routinely observed using photoelectron and resonant Raman spectroscopy. In particular, shakeup satellites can be observed in the two particle spectrum, i.e., when two holes are left in the final state of an atom after electron emission. Satellite s strength can be strongly enhanced in the presence of a resonant intermediate state. For example, in copper atoms, the incident photon can first excite the core 3p electron to the 4s shell the core hole then decays to the 3d shell through the Auger process (with electron ejected from 3d shell) leaving two 3d holes in the final state [48]. For recent reviews of extensive literature the reader is referred to Refe. [49,50]). 

Auger spectroscopy prepares a system in a core-hole state by ionizing radiation and measures the kinetic energy of secondary electrons produced when the highly excited core-hole state makes a radiationless transition to a continuum state with two valence-holes and a free electron. The initial photoelectron and the secondary (Auger) electron make this a two-electron detachment process leading to the two-particle two-hole propagator... 

Electron dynamics of photoionization states in the course of nonadiabatic transition is one of the important molecular processes. It can be applied to the studies on the following dynamical processes Tracking the history of electronic and vibrational states wandering among the excited states in laser fields with designed optical pulses. These time-dependent transient states should be able to be monitored in terms of time-resolved photoelectron spectroscopy [14, 353]. Inner shell ionization from a deep core level and the concomitant electronic state avalanches (decay) towards the hole, which may be accompanied by autoionization, is also quite interesting. In a... 

The development of accurate calculations for the excited states involved in XANES spectroscopy closely mirrors developments in ground-state calculations in molecules and solids. There are, however, several important differences, such as the necessity of a core-hole potential, the core-hole lifetime and final-state photoelectron lifetime effects, possible multi-channel effects, and the energy dependence of the exchange-correlation potential, which complicate the physical model but which may in principle be dealt with, although work continues in all of these areas. 

Auger electron spectroscopy Investigation of the kinetic energy distribution of electrons produced through the decay of a highly excited core hole state. 

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