  Electron-electron thermalization and electron-phonon relaxation processes in
laser-excited solids are often assumed to occur on different timescales. This
is true for the majority of the conduction band electrons in a metal. However,
electron-phonon interactions can influence the thermalization process of the
excited electrons. We study the interplay of the underlying scattering
mechanisms for the case of a noble metal with help of a set of complete
Boltzmann collision integrals. We trace the transient electron distribution in
copper and its deviations from a Fermi-Dirac distribution due to the excitation
with an ultrashort laser pulse. We investigate the different stages of
electronic nonequilibrium after an excitation with an ultrashort laser-pulse of
800 nm wavelength and 10 fs pulse duration. Our calculations show a strong
nonequilibrium during and directly after the end of the laser pulse.
Subsequently, we find a fast thermalization of most electrons. Surprisingly, we
observe a long-lasting nonequilibrium, which can be attributed to the
electron-phonon scattering. This nonequilibrium establishes at energies around
peaks in the density of states of the electrons and persists on the timescale
of electron-phonon energy relaxation. It influences in turn the electron phonon
coupling strength.
