Electron core excitation

Figure 2. Carbon Is core electronic excitations polystyrene (------). Vertical bars...

Figure 3. Energy level diagram illustrating chemical shifts of the core levels and different final state configurations that can be reached by core electron excitation.

The following picture is emerging from this research. Core electron excited states have finite lifetimes and unique characters. The electronic and chemical relaxations are coupled and depend upon the atomic and electronic structure of the molecule, the atomic site of the core hole, and the configuration of the core hole excited state. Experiments leading to an understanding of these dependences are just beginning to be done. 

Research to date has revealed four general types of mechanisms for fragmentation following core electron excitation. These mechanisms are... 

Research on the fragmentation of molecules following core electron excitation was initiated by T. A. Carlson and R. M. White in 1966 (Carlson and White... 

Since synchrotron radiation is polarized, an anisotropic orientational distribution of molecules can be produced by core electron excitation. This distribution is determined by the orientation of the transition dipole moment with respect to the electric vector of the radiation. Information about this alignment and subsequent time evolution is eontained in the angular distributions of fragmentation products resulting from the excitation. Details have been worked out and described in several references for the case of valence electron excitation and ionization (Zare 1972 Yang and Bersohn... 

The electron impact technique has provided valuable information regarding core electron excitation spectra. A laboratory-based apparatus can provide high-quality spectra with a resolution comparable if not superior to that obtained from monochromators used with synchrotron sources. The... 

There are many prospects for research involving chemistry induced by core electron excitation. Opportunities also exist in each of the steps leading to the chemistry. The areas include core electron excitation, autoionization and Auger decay, and fragmentation and other chemical reactions. 

While fragmentation is the dominant chemical reaction induced by core electron excitation of molecules in the gas phase, other reactions such as rearrangements can be expected, and this possibility needs to be investigated. The extent of a Coulomb explosion in a large molecule is not known, and the role of Coulomb localization in the chemistry of isolated molecules needs to be examined further. Electron-multiple ion coincidence experiments are essential in the study of the chemistry because it is necessary to relate specific electronic decay channels to particular fragmentation patterns as identified by the several ions that are produced. 

It is clear that the chemical reactions induced by core electron excitation are atom-specific. They generally depend upon the atomic site of the core hole and the electronic configuration of the core hole excited state. In this sense, the chemistry is selective. The chemistry can be selected by tuning the photon energy to produce particular core hole excited states. In another... 

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