SEMINAR: Physics Seminar

Plasma is the most abundant state of matter in the universe. While it can be found in many astrophysical objects, such as stars and giant planets, it is now also readily accessible in laboratories using intense ultra-short laser irradiation. Dense plasma is highly ionized matter near solid state density. It is relevant, for instance, for the technical realization of inertial confinement fusion.

Transport and optical properties of plasma systems are described by the di-electric function, which is related to correlation functions. Therefore, deduction of plasma parameters from such quantities as the reflectivity, absorption, thermoelectric properties or spectral line shapes is investigated. We will compare theoretical calculations and experimental results. Central quantity of interest is the free electron density since it cannot be measured directly but is crucial for the plasma properties.

The emission and absorption of radiation from dense plasma is one way of gathering information. I will report on Bremsstrahlung, spectral line shapes, reflectivity and Thomson scattering. The features of X-ray spectral lines (K-line profiles) have been investigated by irradiation of solid targets with intense ultra-short pulse laser beams. Theoretical results are obtained using quantum statistical models. For the evaluation of equilibrium auto-correlation functions at arbitrary coupling strength, we can apply MD simulation techniques for classical systems. For finite clusters, we find a more structured frequency spectrum of plasma correlations than a single plasma frequency in bulk. The spatially resolved momentum auto-correlation spectrum is interpreted in terms of collective electron excitation modes. Resonance frequencies of the modes are calculated and interpreted as a rigid oscillation of all electrons and plane wave oscillation. Damping rates are discussed. Size effects of dynamical properties are investigated.