Inverse bremsstrahlung cross section estimated within evolving plasmas using effective ion potentials - Physics > Atomic and Molecular ClustersReport as inadecuate




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Abstract: In this paper we estimate the total cross sections for field stimulatedphotoemissions and photoabsorptions by quasi-free electrons within anon-equilibrium plasma evolving from the strong coupling to the weak couplingregime. Such transition may occur within laser-created plasmas, when theinitially created plasma is cold but the heating of the plasma by the laserfield is efficient. In particular, such a transition may occur within plasmascreated by intense VUV radiation from a FEL as indicated by the results of thefirst experiments performed at the FLASH facility at DESY.In order to estimate the inverse bremsstrahlung cross sections, we usepoint-like and effective atomic potentials. For ions modelled as point-likecharges, the total cross sections are strongly affected by the changing plasmaenvironment. The maximal change of the cross sections may be of the order of 60at the change of the plasma parameters inverse Debye length, kappa, and theelectron density, rho e, in the range: kappa=0-3 A^{-1} and ho e=0.01-1A^{-1}. These ranges correspond to the physical conditions within the plasmascreated during the first cluster experiments performed at the FLASH facility atDESY. In contrast, for the effective atomic potentials the total cross sectionsfor photoemission and photoabsorption change only by a factor of 7 at most atthe same plasma parameter range.Our results show that the inverse bremsstrahlung cross section estimated withthe effective atomic potentials is not much affected by the plasma environment.This observation validates the previous estimations of the enhanced heatingeffect. This is important as this effect may be responsible for high energyabsorption within clusters irradiated with VUV radiation.



Author: F. Wang, B. Ziaja, E. Weckert

Source: https://arxiv.org/







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