Knowledge Bank

We have recorded the negative ion photoelectron (photodetachment) spectra of $Rb2-$ and $Rb3-$ using 2.540 eV photons. Both of these spectra are highly structured, and each exhibits transitions to several electronic states of their corresponding neutrals. The electron affinity of $Rb2$ is found to be about 0.5 eV, in agreement with theoretical predictions. The EA of $Rb3$, on the other hand, appears to be about 0.8 eV, and thus deviates from the value expected based on an extrapolation of theoretical predictions for $Na3$ and $K3$. The goal in these experiments is not only to map the variation of alkali cluster electron affinities as a function of cluster size, but also to chart the changing electronic states of neutral alkali clusters with size. The hope is that we may eventually be able to start to see the evolution of band structure in these systems.