Ion-ion correlation impacts on electron-ion collision rates in plasmas

Ultracold plasmas can be created at sufficiently cold temperatures that spatial correlations in the electron and ion components can become significant with respect to many plasma properties in the so-called strong coupling regime. In recent experimental work, we measured a discrepancy between predicted and measured electron-ion collision rates. Subsequent simulations of this experimental measurement have indicated that ion-ion correlations need to be taken into account in computing the electron-ion collision rate. This is despite the fact that there is a mass ratio of approximately $10^5$ between the ion and electron masses in the ultracold plasma. We discuss the significance of these results in the context of both ultracold plasmas and other plasmas in general.