Inverse bremsstrahlung heating rate in atomic clusters irradiated by femtosecond laser pulses

In the interaction of atomic clusters with femtosecond laser pulses, nanoplasmas with high density and high temperature are created. The heating is mainly determined by inverse bremsstrahlung (IB) due to electron-ion collisions. In many approaches for the calculation of the IB heating rate such as the Born approximation, large-angle scattering events are underestimated. However, rescattering events of an electron on the same atomic ion play an important role because they increase the amount of energy exchanged between the electrons and the laser field. In noble gas plasmas, the electron-ion interaction is often considered to take place between point-like particles. For typical noble gas clusters studied in experiments, one is advised to take into account not only the screening by the surrounding plasma medium but also the inner structure of the ions what can be accomplished by the use of appropriate model potentials. In the present paper, the IB heating rate is calculated from the classical simulation of individual electron trajectories. Results are presented for xenon clusters and argon clusters with different degree of ionization. Especially for higher energies, the consideration of the ionic structure increases the heating rate compared with the scattering on point-like particles. The Born approximation, however, overestimates this effect. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694784]