Interaction of photons with plasmas and liquid metals-photoabsorption and scattering

Formulae for describing the photoabsorption and the photon scattering by a plasma or a liquid metal are derived in a unified manner. It is shown how t he nuclear motion, the free-electron motion and the core-electron behaviour of each ion in the system determine the structure of the photoabsorption a nd scattering in an electron-ion mixture. The absorption cross section in t he dipole approximation consists of three terms which represent the absorpt ion caused by the nuclear motion, the absorption owing to the free-electron motion producing optical conductivity or inverse Bremsstrahlung and the ab sorption ascribed to the core-electron behaviour of each ion with the Doppl er correction. Also, the photon scattering formula provides an analysis met hod for experiments observing the ion-ion dynamical structure factor (DSF), the electron-electron DSF giving plasma oscillations and the core-electron DSF yielding the x-ray Raman (Compton) scattering with a clear definition of the background scattering for each experiment, in a unified manner. A fo rmula for anomalous x-ray scattering is also derived for a liquid metal. At the same time, Thomson scattering in plasma physics is discussed from this general point of view.