Autoionization electrostatic

These are produced by autoionization transitions from highly excited atoms with an inner vacancy. In many cases it is the main process of spontaneous de-excitation of atoms with a vacancy. Let us recall that the wave function of the autoionizing state (33.1) is the superposition of wave functions of discrete and continuous spectra. Mixing of discrete state with continuum is conditioned by the matrix element of the Hamiltonian (actually, of electrostatic interaction between electrons) with respect to these functions. One electron fills in the vacancy, whereas the energy (in the form of a virtual photon) of its transition is transferred by the above mentioned interaction to the other electron, which leaves the atom as a free Auger electron. Its energy a equals the difference in the energies of the ion in initial and final states ... 

Values are collected in Table 5.4 for the electronic part of the electrostatic interaction. It is clear that this interaction will give rise either to perturbations or to predissociations depending on whether the interaction occurs between discrete states or discrete and continuum states. In the above example, concerning the N2 1IIU states of Worley s third series, it was shown that the electrostatic interaction can also give rise to autoionizations (Chapter 8). 

These /-levels, in addition to being weakly predissociated, are also very weakly autoionized (see also Fig. 8.23). Another example appears in the spectrum of Li2 (Chu and Wu, 1988). In many other cases, decay by predissociation can be very fast, particularly for electrostatic predissociations (see Tables 7.3 and 7.4). For example, in the spectrum of the NO molecule, most 2Il Rydberg states are predissociated by the vibrational continuum of the B2n valence state so rapidly that autoionization cannot compete (Giusti-Suzor and Jungen, 1984). 

Figure 8.14 Photoionization cross-section of N2 taken at 77 K with a resolution of 0.016 A (from Dehmer, et al., 1984). The first members of the v = 1 series are vibra-tionally autoionized by the v+ = 0 continuum of Nj X2Sg. For n > 14, anomalies result from indirect electrostatic autoionization (from Giusti-Suzor and Lefebvre-Brion, 1984).

Figure 8.18 Schematic illustration of the electrostatic autoionization of the 1Itu Rydberg states converging to the A2nu state of Nj by the continuum of the X2Sj state, (a) Worley-Jenkins Rydberg series, (b) Worley s (third) Rydberg series.

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