The evolution of the electron distribution in a metal irradiated by an ultrashort laser pulse is described on the basis of numerical solution of the equation for the one-particle density matrix. The excitation mechanism is attributed to the laser quanta absorption in electron collisions with both longitude and transverse-acoustic phonons. It is shown that the absorption is mainly determined by the umklapp processes. The electron relaxation is due to electron-electron collisions taken into account using the relaxation-time approximation. The agreement with the experiment of Fann et al. [Phys. Rev. B 46, 13 592 (1992)] is good.

• Received 15 October 1998

DOI:https://doi.org/10.1103/PhysRevB.60.3279