Effect of competition between relaxation and decay on the Auger-photoelectron coincidence spectroscopy (APECS) spectra of Pd metal

The high-resolution coincidence M45 photoelectron spectra and coincidence M45-VV Auger-electron spectroscopy (AES) spectra of Pd metal reported by Butterfield et al. [M.T. Butterfield, R.A. Bartynski, S.L. Hulbert, Phys. Rev. B66 (2002) 115115] are analyzed by a many-body theory. MX is the atomic shell Mx. The Auger-photoelectron coincidence spectroscopy (APECS) spectra provide the evidence of the rapid delocalization of the valence hole created in Pd metal either by the M45 shakeup or by the M4-M5V Coster-Kronig transition before the M45-hole or the M5-hole decays. The M45 shakeup state relaxes to the M45 main-line state before the M45-hole decays. As a result, the singles (noncoincidence) M45-VV AES spectral line shape becomes the sum of the intrinsic coincidence M5-VV AES one and the intrinsic coincidence M4-VV one, weighted by a M5-VV to M4-VV ratio of 1.0:0.7, which agrees well with the theoretical M45-level ionization cross section ratio of 1.0:0.69. A high-resolution APECS can reveal the core-hole dynamics in much more detailed manner than conventional noncoincidence techniques.