Richardson–Laue–Dushman equation

The Richardson-Laue-Dushman (RLD) equation predicts current density due to thermal emission, generally from metals that, through the application of coatings such as barium to a porous tungsten base, have a low work function. For the transmission probability, observe that fields for typical thermal emission measurements are comparatively weak, so weak in fact that electrons even a wee bit below the barrier maximum /a + $ are prevented from escaping. Retarding potential (RET) and saturation current (SAT) measurements are two methods of measuring the current density from a hot source. They are different in that the RET measurements assess the temperature-independent thermal constants, but the SAT experiments give an A coefficient that must be reduced to account for changes in the work function due to a temperature variation.