Distribution of oscillator strengths of the hydrogen atom in dense media and plasmas

The photoionizaton cross section and distribution oscillator strengths of the hydrogen atom in a dense plasma are computed using a simple model potential which includes the effect of the fields of surrounding particles on the electron in an atom. It is shown that a ''transparency window'' appears near the photoionization threshold of the atom and that there is a redistribution of the energy in the absorption (emission) spectra at high frequencies. The sum of the oscillator strengths over the spectrum is close to unity if the first excited state does not fall into the perturbation region. The limits of applicability of these results are discussed.