An improved rubidium consumption model for discharge lamps used in rubidium frequency standards

The model equation for Rb consumption C is C=A+B√T, where T is lamp operating time and B is an experimentally determined diffusion-related coefficient. A has been assumed to be loss resulting from a virtually instantaneous reactive process. In some of present data sets, consumption measurements indicate that the reactive cleanup is time-dependent. This dependence is well described by a term with two constants, A´ and D, where A´(1-exp(-DT)), resulting from first-order reaction kinetics. Including this term improves the ability to predict long-term Rb consumption on the basis of a limited amount of experimental data