Characterization and measurement of a nonequilibrium temperature-like variable in irreversible thermodynamics

The question of the definition and measurement of nonequilibrium temperature is considered. Its characterization in the framework of an informational statistical thermodynamics is done, and its dependence on the irreversible fluxes that develop in systems out of equilibrium is proved. A particular analysis for the case of a highly photoexcited plasma in semiconductors is presented, where the nonequilibrium temperature of the carriers, usually referred to as the carriersʹ quasi-temperature, can be measured in experiments of modulation optical spectroscopy. Comparison of theory and experimental data seems to point to a corroboration of the identification of the nonequilibrium temperature with the quasi-temperature as well as its dependence on the energy flux, as predicted by the phenomenological and statistical thermodynamic theories.