On the thermal broadening of core levels in metals due to many‐electron effects
Ferrell's expression for the XPS lineshape is derived in a formalism which explicitly takes the electron—electron interaction into account. Also the corresponding expression for X-ray absorption is given. In the presence of other broadenings, which are comparable or larger than kT, the electronic part of the core-level broadening in XPS is indistinguishable from a Gaussian. This Gaussian broadenin