Abstract
This paper proposes a nonequilibrium model to describe the ultrafast laser-excited electron photofield emission from a metallic surface with an applied dc voltage. Using a microscopic kinetic approach based on Boltzmann's equation, we determine the nonequilibrium electron distribution due to the ultrafast laser excitation on metal and calculate the time dependence of the emitted electron charges and current density. Our calculation is able to explain the prior experimental observations without using the optical-field emission, which was disputed among the experiments. Inconsistency of the prior models used to explain the experimental results is discussed.