Configuration interaction, autoionization

The advances in this field are related with the development of the theory of configuration interaction between different excitation channels in nuclear physics including quantum superposition of states corresponding to different spatial locations for interpretation of resonances in nuclear scattering cross-section [7] related with the Fano configuration interaction theory for autoionization processes in atomic physics [8],... 

There are more complicated branches which are due to final-ionic-state configuration interaction. These have been omitted for simplicity (for details see [Sch92a]). Some of these final states proceed further via a second-step autoionization or Auger decay for example,... 

D. R. Herrick, O. Sinanoglu, Comparison of doubly-excited helium energy levels, iso-electronic series, autoionization lifetimes, and group-theoretical configuration-mixing prediction with large-configuration-interaction calculations and experimental spectra, Phys. Rev. A 11 (1975) 97. 

Autoionization by configuration interaction is usually quite fast, and there are many cases in which it predominates over predissociation so that the thresholds of excited states are hidden. However, ethylene " provides an example in which predissociation is sufficiently rapid that the thresholds for the first excited electronic state are apparent in the cross section. 

Another type of such coupling is the configuration interaction (CI) between a true discrete excitation and a continuum excitation. This autoionization phenomenon is clearly within the TDLDA framework, A nice example can be found in copper where 3d -> ef, ep excitations interfere with the 3p -> 4s transition, The resulting 3d partial photoionization cross section is shown in Figure 8, In addition to the prominent Fano line shape, an overall diminultion (relative to the LDA) of the cross section is found due to intrashell 3d polarization. The interesting dip around 80 eV is again a Cl effect, but this time the 3d ef,ep excitations interfere with the continuum channels, 3p es,ed. 

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