Inversion of atomic resonance transitions by electron collisional dissociation

Population inversion of several resonance transitions in the rare-earth atom thulium has been achieved by electron collisional dissociation of TmI3 molecules in a fast electric discharge configuration. The inversion manifests itself by a strong spiking behavior during the initial current rise and lasts for several nanoseconds. Results of a model calculation of this inversion process for resonance lines support our experimental findings.