UV-photoelectron spectroscopy at highest resolution - Direct access to lifetime effects in solids?

Lineshapes and linewidth in angle-resolved photoemission spectra from solid surfaces contain a wealth of contributions from e.g. the photohole lifetime, the lifetime of the final state electron, and from their respective interactions with phonons and lattice imperfections. In addition, finite energy and angular resolution contribute to the experimentally observed linewidths. Using photoelectron spectra from bulk and surface state transitions on copper as an example, we discuss to which extent the various contributions may be distinguished experimentally. The results indicate that relevant spectroscopic information can be directly derived from such studies at very high resolution. This will lead beyond the kinematical analysis of photoelectron data in terms of band structures and may enable us to extract quantities which refer to the dynamical properties of the many-electron system.