Inner-shell excitation

Inner-shell excitation of the Li-like ion core is the second mechanism to populate the doubly excited levels. For the three electron system, the cascade effect between doubly excited levels is negligible compared to dielectronic recombination. This is justified by the fact that for highly charged ions the states with higher n, n 3, have large initial populations, so therefore the contribution due to the cascade is negligible. The emission of the satellite line is then  

Even within the independent electrom approximation, it is obvious that there must exist inner-shell excitation spectra, and that their energy must extend well above the first ionisation potential. This arises from the simple fact that one can choose which electron is excited it does not necessarily have to be the valence electron, and the inner electrons, being more strongly bound, require photons of higher energy to excite them. Since the valence electron extends furthest out from the atomic core, one is tempted to think that it is always the easiest electron to excite, both because it can more readily interact with an external field (higher transi- 

If the quasiparticle approximation works well, then this is a sign that the independent particle model is trustworthy. If one is looking for manifestations of the many-electron character of atoms, then the greatest interest attaches to situations where in fact the quasiparticle picture begins to break down. From this perspective, the excitation of very deep inner shells is not the most interesting situation it is more likely that the concept of a hole will lose validity for the outermost inner shells, although the situations in which this occurs are actually quite specific. 

There exist theoretical models which confirm the general argument just presented. Since the details are somewhat complex [301], we summarise their results in graphical form in fig. 7.1. 

In case (a) of the figure, we show a typical photoelectron spectrum containing just one line, which corresponds to the excitation of one electron and results in just one ionic state. In case (c), the typical X-ray spectrum is dominated by one line, which represents the quasiparticle, with a few 

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Firstly, the energy losses of the incident electrons which produce the inner shell excitations may be detected as peaks in electron energy loss spectroscopy (EELS). The elecrons transmitted by the specimen are dispersed in a magnetic field spectrometer and the peaks, due to K, L and other shell excitations giving energy losses in the range of 0-2000eV, may be detected and measured. 

Dipole oscillator strengths form important input into all stopping models based on Bethe or Bohr theory. Emphasis has frequently been on total /-values which show only little sensitivity to the specific input. More important are differential oscillator-strength spectra, in particular at projectile speeds where inner-shell excitation channels are closed. Spectra bundled into principal or subshells [60] are sufficient for many purposes, but the best available tabulations are based on analysis of optical data rather than on theory, and such data are unavailable for numerous elements and compounds [61]. 

Hitchcock, A. P., and Mancini,D. C. (1994). Bibliography of atomic and molecular inner-shell excitation studies. J. Electron Spectrosc. Relat. Phen. 67,1-132. 

The second class consists of processes which can be described in a two-step model by an inner-shell excitation or ionization process followed by a subsequent... 

For autoionization following inner-shell excitation such a classification neglects the competing and interfering process of direct photoionization leading to the same final state. It would be more appropriate to consider autoionization as a resonance feature embedded in the ionization continuum of main and satellite photoprocesses. 

A similar process selection is possible for inner-shell excitation or double excitation and subsequent autoionization decay (described in the first case by a cross section of the first step, cr, and in the latter case by o ). These processes occur only at specific photon energies hvr (subscript r for resonance), and the kinetic energy of electrons from the autoionization decay is then fixed by... 

Transition energies for inner-shell excitation of the C02 molecule... 

M. Isaacson, Interaction of 25keV electrons with the nucleic acid bases, Adenine, Thymine, Uracil. II. Inner shell excitation and inelastic scattering cross sections, J. Chem. Phys. 56 (1972) 1813. 

A wide variety of plasma diagnostic applications is available from the measurement of the relatively simple X-ray spectra of He-like ions [1] and references therein. The n = 2 and n = 3 X-ray spectra from many mid- and high-Z He-like ions have been studied in tokamak plasmas [2-4] and in solar flares [5,6]. The high n Rydberg series of medium Z helium-like ions have been observed from Z-pinches [7,8], laser-produced plasmas [9], exploding wires [8], the solar corona [10], tokamaks [11-13] and ion traps [14]. Always associated with X-ray emission from these two electron systems are satellite lines from lithium-like ions. Comparison of observed X-ray spectra with calculated transitions can provide tests of atomic kinetics models and structure calculations for helium- and lithium-like ions. From wavelength measurements, a systematic study of the n and Z dependence of atomic potentials may be undertaken. From the satellite line intensities, the dynamics of level population by dielectronic recombination and inner-shell excitation may be addressed. 

The information on the relative abundances of ionization stages is found by detailed modeling of the spectra. The density of Li-like ions is obtained from the intensity of doubly excited satellites, which are predominately populated by collisional inner-shell excitation with small contributions of dielec-... 

The k and j satellites are the strongest dielectronic satellites to the He-like lines, the q, r, s and t satellites have strong contributions due to inner-shell excitation from the Li-like ground state. Besides the dominant collisional excitation of He-like ions in the ground state, recombination processes (radiative, dielectronic and charge exchange) of H- and He-like ions, inner-shell excitation of the Li-like ions and, in the case of the z line, also inner-shell ionization process contribute to the intensity of the He-like lines. We will discuss these processes in detail. 

In contrast to the density measurements of Li-like ions by means of inner-shell excitation, the spectra provide information not directly on the density... 

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