Shapes and Interference Effects in Autoionization Spectroscopy

Line Shapes and Interference Effects in Autoionization Spectroscopy 

Spectra of autoionization lines are often very different from normal optical spectra in that the line shapes are strongly influenced by interference effects. Symmetric line shapes on a low background signal are the exception. Two different types of processes can contribute to the ionization signal (i) the direct ionization which leads to a continuous electron spectrum and which is especially important when projectiles with high velocities or photons are initiating the ionization process (ii) excitation and decay of 

Here a summation over final states lf and an averaging over initial states fii with a weighting factor w fii) has been performed. Cj is a direct and C are autoionization amplitudes, which depend on the energy e (of impinging projectiles or ejected electrons) and detection angles (i, ) determined by the experiment. The energy-dependent relative phases of the complex amplitudes C determine to a large extent the shape of the observed lines. 

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