Photoabsorption in dense plasmas

A common approach to bound and free electrons in photoabsorption calculation based on the first order of the cluster expansion is discussed. The formalism allows one to include the important part of dynamic correlations between all electrons. Such treatment is necessary in photoabsorption calculations at high plasma densities in order to account for pressure ionization and channel mixing between the particle-hole and collective transitions. An example of a standard calculation for iron plasma at 20 eV temperature and several densities is discussed. Limitations of the existing models at high plasma densities are indicated in this example. Photoabsorption experiments at conditions similar to the ones of the example will be possible using the large lasers expected in the future.