Increased phonon broadening of XPS lines of metals due to finite core-hole lifetime

The author generalizes the solution of the independent boson model to take the finite lifetime of the core hole into account. The generalized solution is compared to the conventional convolution of the infinite lifetime spectral function with a Lorentzian lifetime broadening function. The generalized solution reduces to the conventional convolution in two limits. However, the new solution predicts appreciable phonon broadening for simple metals. Rough estimates of this new effect are compared with recent experimental results on XPS lines.(12 refs)