Electron and phonon relaxation in metal films perturbed by a femtosecond laser pulse

A theoretical investigation of the electron and phonon time-dependent distributions in an Ag film subjected to a femtosecond laser pulse has been carried out. A system of two coupled time-dependent Boltzmann equations, describing electron and phonon dynamics, has been numerically solved. In the electron Boltzmann equation, electron-electron and electron-phonon collision integrals are considered together with a source term for laser perturbation. In the phonon Boltzmann equation, only electron-phonon collisions are considered, neglecting laser perturbation and phonon-phonon collisions. Screening of the interactions has been accounted for in both the electron-electron and the electron-phonon collisions. The results show the simultaneous electron and phonon time-dependent distributions from the initial non-equilibrium behaviour up to the establishment of a new final equilibrium condition.