Analysis of the Auger-photoelectron coincidence spectroscopy (APECS) spectra of metallic Pd, Ag, and Sn

The M45-level photoelectron spectrum of Ag metal measured in coincidence with the M45-VV(1G) Auger-electron line is analyzed by taking into account the possibility of the M4-M5-VV Coster-Kronig (CK)-transition preceded Auger transition. We denote the atomic shells Mx(Mxy) and Nxy (x, y = 4,5) by MX(MXY) and V, respectively. The M4-M5 CK-transition rate is very small. The M45-VV Auger-electron spectra of metallic Pd and Sn measured in coincidence with the M4 (or M5)-level photoelectron line are analyzed. The M4-M5 CK-transition rates are also very small in metallic Pd and Sn. The coincidence Auger-electron line previously interpreted as the M4-M5-VV (or M4-M5V-VVV) Auger-electron line is largely due to the inelastically scattered M5-level photoelectron background beneath the M4-level photoelectron line. The APECS spectrum of Pd metal shows the first evidence of the M5V-VVV transition of the localized M5V shakeup two-hole state. The intensity ratio of the inelastically scattered Auger-electron background to the M5-VV Auger-electron main line of Ag metal measured in coincidence with the inelastically scattered M5-level photoelectron background beneath the M4-level photoemission line increases, as compared to that measured in coincidence with the M5-level photoelectron main line. This is because when the probability of the photoelectron being inelastically scattered increases, that of the Auger electron emitted by the same ionized atom, being inelastically scattered increases. In other words the photoelectrons and the Auger electrons are originated from the deeper atomic sites (longer pathlength).