Partial channel photoionization cross section

Figure 15. Partial-channel photoionization cross sections for 2bj, 5aj and 2b2 orbitals of H2S obtained in static-exchange approxi tlon.

The structure of the p-p propagator is very similar to that of G. This popagator describes the simultaneous annihilation of two electrons from the system as well as the simultaneous attachment of two electrons to the system. In particular, the pole positions of the first and second part of FI represent double ionization potentials (DIP) and double attachment energies. DIPs, EAs, and IPs are, of course, important quantities of electronic systems. But not only the pole positions are related to experiment. The residue amplitudes and contain relevant information on the single and double ionization and attachment (or scattering) processes. For instance, the partial-channel photoionization cross section for production of molecular ions in the nth state reads in the sudden approximation ... 

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. 

In 2p photoionization in magnesium the partial cross section o2p is large compared to o3s and photoionization channel will be small. (In contrast, the effect of 2p photoionization on the 3s and 2s channels can be expected to be significant.) More important here is the continuum mixing of Fig. 5.10(a) with es and ed partial waves. Since Dd is larger than DS, it is essentially the Dd -amplitude which modifies the Ds -amplitude. This can be verified from Table 5.1 by comparing the RRPA results with those of the HFf P) calculation DS is increased while Dd remains nearly the same. 

Fig, 20. Double photoionization of argon calculated by Carter and Kelly, ref. 111. Partial-wave cross sections are given for four different 3p ->k k channels in both dipole length (solid curves) and velocity (broken curves) approximations. 

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