  We calculate the dielectric response of excited crystalline silicon in
electron thermal equilibrium by adiabatic time-dependent density functional
theory (TDDFT) to model the response to irradiation by high-intensity laser
pulses. The real part of the dielectric function is characterized by the strong
negative behavior at low frequencies due to excited electron-hole pairs. The
response agrees rather well with the numerical pump-probe calculations which
simulate electronic excitations in nonequilibrium phase immediately after the
laser pulse irradiation. The thermal response is also compared with the Drude
model which includes electron effective mass and collision time as fitting
parameters. We find that the extracted effective masses are in the range of
0.22-0.36 and lifetimes are in the range of 1-14 fs depending on the
temperature. The short Drude lifetimes show that strong damping is possible in
the adiabatic TDDFT, despite the absence of explicit electron-electron
collisions.
