Determination of the hole lifetime from photoemission: Ti 3d states in TiTe2

The electron hole spectral width Gamma(h) of Ti 3d states in layered TiTe2 and the inverse lifetime V(i) of the photoelectron final states are determined from experiment within the one-step theory of photoemission. The condition for the possibility of separating the effects of Gamma(h) and V(i) is a strongly non-free-electron character of the final states. The resulting drastic changes of the line shape with photon energy are experimentally observed and explained by an ab initio theory. A nonmonotonic dependence of V(i) on the final-state energy is observed; it is shown to reveal the real space structure of the complex electron self-energy.