Interaction of ultra‐short laser pulses with clusters: short‐time dynamics of a nano‐plasma

We study the dynamics of the interaction of short infrared laser pulses with large rare‐gas clusters. Special attention is given to the microscopic atomic collision dynamics in order to explain the efficient heating of the quasi‐free electrons in the nano‐plasma formed during the interaction. In the framework of our mean‐field classical transport simulation we are able to explain the emission of characteristic x‐rays at moderate laser intensities (I ∼ 1015W cm−2) where the ponderomotive energy of the electrons is by far to low to allow for the creation of inner‐shell vacancies. We identify large‐angle elastic electron‐ion scattering as an important heating mechanism at moderate laser intensities.