Thermoelectron emission of iridium exposed to fast pulsed heating

It has been established that rapidly heating iridium by a high-density electric current $(j = 10^6$ A/cm$^2)$ gives rise to two pulses of unusually strong thermoelectron emission (as opposed to one in analogous experiments with tungsten and nickel). This phenomenon can be explained by a hypothesis on nonequilibrium thermal defects in the metal. According to this hypothesis, the large emission from the first pulse is due to the effect of interstitial atoms of dissolved gases or other impurities, and the second is due to a nonequilibrium concentration of interstitial atoms of the metal itself. In both cases, the decay of the enhanced emission to an equilibrium value after the rapid heating ceases is related to the annihilation of the interstitial atoms (of both impurities and the metal itself) by vacancies which diffuse inside the emitter from the surface.