New approximation for calculating free-free absorption in hot dense plasmas
- 1 June 1996
- journal article
- research article
- Published by Cambridge University Press (CUP) in Laser and Particle Beams
- Vol. 14 (4), 731-748
- https://doi.org/10.1017/s0263034600010430
Abstract
We propose a model for calculating free-free absorption (inverse bremsstrahlung) in hot dense plasmas. This model writes the total Gaunt factor as the product of a static factor and a dynamic factor. The treatment of the static part is based on a relation between the absorption cross section and the elastic scattering cross section, which is exact for very low frequencies and becomes asymptotically correct when the Born approximation is valid. Generalizing this relation provides an expression of the absorption cross section Q(k, k′), which depends on the initial and final wave vectors k and k′, as an integral of a unique function S*(k). The calculation of nondiagonal matrix elements (k ≠ k′) is thus avoided. The analytic summation of the high angular momenta in the partial wave expansion of the cross section makes possible to apply the model in the limit of weak electron screening. The collective effects are accounted for in a dynamic Gaunt factor and in an index of refraction different from unity. Numerical results for the Gaunt factor in cesium are presented and discussed. An application to the mean opacities of carbon is also shown.Keywords
This publication has 11 references indexed in Scilit:
- Review of the third international opacity workshop and code comparison studyJournal of Quantitative Spectroscopy and Radiative Transfer, 1995
- PhotoabsorptionKedge of shock compressed aluminumPhysical Review Letters, 1993
- Radiative atomic Rosseland mean opacity tablesThe Astrophysical Journal Supplement Series, 1992
- Time-dependent density-functional theory of light absorption in dense plasmas: Application to iron plasmaPhysical Review A, 1985
- Calculation of free-free Gaunt factors in hot dense plasmasPhysical Review A, 1983
- Density-functional approach to local-field effects in finite systems: Photoabsorption in the rare gasesPhysical Review A, 1980
- Correct values for high-frequency power absorption by inverse bremsstrahlung in plasmasPhysics of Fluids, 1973
- Radiative Absorption Cross Section of an Electron in the Field of an Argon AtomPhysical Review B, 1966
- High-Frequency Conductivity and the Emission and Absorption Coefficients of a Fully Ionized PlasmaPhysics of Fluids, 1962
- Electron Radiative Transitions in a Coulomb Field.The Astrophysical Journal Supplement Series, 1961