Electron-ion recombination in strongly coupled cold plasmas under nonequilibrium conditions

We discuss the dynamics of recombination of an expanding ultracold plasma into highly excited Rydberg states, with emphasis on the influence of possible strong coupling between the charges and the nonequilibrium character of the electronic component. While the former does not significantly affect recombination in current experimental scenarios, the latter is shown to have a considerable influence on the system dynamics. We derive correction factors quantifying the deviation of collision rates from their respective equilibrium values. The experimentally observed unexpectedly high recombination rate at long evolution times can be reproduced by a proper inclusion of these effects without the need to invoke alternative, previously suggested mechanisms, such as an 'adiabatic motional recombination' or the development of very strong electron correlations by collisional cooling