  Ultrafast laser measurements probe the non-equilibrium dynamics of excited
electrons in metals with increasing temporal resolution. Electronic structure
calculations can provide a detailed microscopic understanding of hot electron
dynamics, but a parameter-free description of pump-probe measurements has not
yet been possible, despite intensive research, because of the phenomenological
treatment of electron-phonon interactions. We present ab initio predictions of
the electron-temperature dependent heat capacities and electron-phonon coupling
coefficients of plasmonic metals. We find substantial differences from
free-electron and semi-empirical estimates, especially in noble metals above
transient electron temperatures of 2000 K, because of the previously-neglected
strong dependence of electron-phonon matrix elements on electron energy. We
also present first-principles calculations of the electron-temperature
dependent dielectric response of hot electrons in plasmonic metals, including
direct interband and phonon-assisted intraband transitions, facilitating
complete theoretical predictions of the time-resolved optical probe signatures
in ultrafast laser experiments.
