Intense VUV laser cluster interaction in the strong coupling regime

The interaction of noble gas clusters with intense, VUV radiation is investigated by molecular dynamics simulations. It is shown that the free-electron laser cluster interaction creates a strongly coupled plasma. A new heating mechanism is identified that is more efficient than inverse Bremsstrahlung heating and explains the observation of unusually high charge states in recent experiments at DESY. The heating mechanism is a consequence of the strongly coupled plasma dynamics, in which collisional processes are strongly modified. Energy absorption takes place in the following cycle: many-body collisions, resulting in an enhanced recombination of free electrons to exited states, and subsequent reionization.