A new approach to the complete photoionization experiment, by means of a coincidence measurement between autoionized electrons and polarized fluorescent photons, in the region of the 3p-3d resonance in calcium

Abstract

By using synchrotron radiation to excite calcium atoms in the 3p-3d resonance region, excited calcium ions are generated. In the first measurement of this kind, we have measured the polarization of the fluorescent photons which result from the decay of these ions, in coincidence with the corresponding angle-resolved photoejected electrons. By combining this with the angular distribution parameter for these same electrons, measured in a separate experiment, we are able to calculate for this specific case, within the assumption of LS coupling, the ratio of the dipole amplitudes for the outgoing waves and their phase difference.

Coherence and correlations in photoinduced Auger and fluorescence cascades in atoms

“…The electron-photon coincidence (e-coincidence) technique has been used for studying the Auger (autoionization) electron-fluorescence photon cascades in metallic vapors, beginning with the pioneering work by Beyer et al (1995). For these coincidence measurements, the experimental set-up is shown in Fig.…”

“…This arrangement was used both, for non-coincidence measurements and for those measurements where the autoionization electron and the fluorescence photon were detected in coincidence. Experiments with this set-up have been carried out for the excitation region of the 3p-3d resonances in Ca (Beyer et al, 1995 and 4p-4d resonances in Sr (West et al, 1998;Ueda et al, 1998).…”

“…With the advent of new SR sources these studies were extended, especially for the noble gas atoms (for example, O'Keeffe et al, 2004;Schartner et al, 2005 and references therein). The angular correlations between the ejected electron and the polarized fluorescence, measured in the 1990s (Beyer et al, 1995Ueda et al, 1998), provided a method of obtaining a very rich or sometimes even complete information on the Auger decay.…”

“…Besides, more information is available on the decay amplitudes from the coincidence experiments. Observations of fluorescence in coincidence with the Auger or autoionizing electron can constitute a complete experiment in certain cases (Beyer et al, 1995). A theoretical description of the angular correlations between the photo/Auger electron and polarized fluorescence photons has been developed by Kabachnik and Ueda (1995).…”

“…In contrast to the rather common non-coincidence measurements, the coincidence angle resolved experiments, which involve two Auger electrons from a cascade, are still rather scarce Wehlitz et al, 1999;Turri et al, 2001;Ueda et al, 1999aUeda et al, , 2001Ueda et al, , 2003bDa Pieve et al, 2005). Furthermore, only a few experiments were reported in which an emitted Auger electron was detected in coincidence with polarized fluorescence photons (Beyer et al, 1995Ueda et al, 1998).…”