The fine structure of IL is the set of features in its contour in the energy
interval 0 < E < (Ep- ). The given energy interval consists of two regions - extended
(0 < E < (Ep-)-50eV) and nearthreshold (adjacent to IL). The features with
magnitude in N(E) comparable with the magnitude of IL, are usually called IL
sattelites [Ref 3].
The fine structure originates from complicated effects of electron interaction
with the medium. These effects may fall into the following groups:
The first group deals with the many electron structure of atoms –
multiplet line structure,
configurational interaction,
shake-on and shake-off, etc.)
[Ref 3]
The second group owes to the electron interaction, simultaneous or
sequential, with many atoms in the condensed matter – multiple scattering, interfacial
refraction, coherent electron scattering (due to short and long range order) which
gives rise to extended fine structure of IL, nonlocal interaction,
collective
excitations of IL plasma sattelites, the effects of chemical surrounding,
the effects of band structure, etc. [Ref 3].
IL sattelites arising from excitations of surface and bulk plasmons are almost
universally observed and are the most intensive. They are situated in the nearthreshold
fine structure region and are separated by  and  from IL.
Here and are the excitation enrgies of surface and bulk plasmons respectively. Their values
are usually in the range of 5..30 eV [Ref 3].
Extended fine structure of ionization spectrum has a periodic nature. It
is connected with interference and diffraction of de Broigle waves belonging to the
electron which is throwed out of the core level and to the primary electron. These
interference and diffraction take place on the atoms of the first and the following
coordination spheres. Thus, it is possible to determine interatomic distances in the
presurface layer by investigating the extended fine structure [Ref 3, Ref 7]. A
more detailed account of the influence of all those effects on the IS fine structure is
given in [Ref 3].
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