PcL A threshold photoelectron specmm and its component spectra of Auger cascades aRer AI K-shell photoionization have been measxed by wincidenoes between threshold photoelectrons and residual ions of Lhe cascades. These spectra exhibit remarkable profiles of postcollision interaction effects due to the Auger cascades. The peak shift increases gradually according to the tims of interactions. but the peak broadening is almost indepndent of the times of interactions. Tbese p m 6 k a~ analysed in terms of a simple model expressing the pmbability of A u p eleftmu emissions by statistical w e i g hIn near-threshold inner-shell photoionization of atoms, the subsequent Auger decay might be influenced by the presence of a slowly receding photoelectron. This influence is called post-collision interaction ( F a ) .Close to the threshold, the slower photoelectron shields the doubly charged atomic ion so that the faster Auger electron gains energy and, as its counter

A threshold photoelectron spectrum and its component spectra of Auger cascades following Kr -shell photoionization have been measured by a threshold photoelectron-ion coincidence technique. These spectra exhibit characteristic profiles of post-collision interaction effects induced by the Auger cascades. Peak shifts of the profiles increase gradually according to the times of the interactions, but peak widths of the profiles are almost independent of the times of interactions. These characteristics are analysed in terms of a simple model based on the assumption that double-Auger (Auger shake-off) decays reduce the effective number of steps of the Auger cascades.

Yield spectra of multiply charged ions in coincidence with threshold electrons (Ekin⩽0.03 eV) have been measured near the 4p-shell ionization region of Xe. The coincidence spectra of Xe3+ and Xe4+ ions as a function of photon energy exhibit characteristic profiles induced by post-collision interactions in Auger cascades following 4p-shell threshold ionization of Xe. Peaks of the profiles shift from the nominal 4p-shell threshold, and those shapes are asymmetric and broadened. The profiles have the same peak-shifts and the same peak-widths in both Xe3+ and Xe4+ coincidence spectra. Based on the properties of the profiles, it is concluded that both of these ions result from two-step Auger cascades. Furthermore, it is found that Auger shake-off (i.e. double Auger) decays play a significant role in the cascades following 4p-shell ionization of Xe.

Multiple photoionization cross sections of Kr have been measured in the photon energy region of 90-260 eV. Partial cross sections for valence ionization, 3d ionization and 3d shake (shake-up and shake-off) have been derived from these multiple photoionization cross sections. The experimental results are compared with a recent theoretical calculation.

The yield spectra of Xe" and Xe3+ ions near the 4d ionization limits have been measured by a threshold electron-photoion coincidence method. These spectra consist of some prominent peaks corresponding to the 4d-'np Rydberg states and two dominant peaks corresponding to 4d threshold ionization. It is proposed that threshold-electron emission from the inner-shell resonance states is due to not only shake-off (e.g. Xe 4d-'6p-+ Xe2' Sp-') but also two-step autoionization (e.g. Xe 4d-'6p+ Xei 5s-'5p-'7p+ XeZL SsCISp-'). The two-step autoionization process plays an important role in decays from the lower n Rydberg states. Two dominant peaks somewhat above the 4d ionization limits show the effect of post-collision interaction, namely, shifts of peak positions and asymmetric profiles. The shifts are almost the same in the Xe'+ and Xe'+ spectra