In-medium effects at low temperatures in the photon bremsstrahlung

The influence of the dense nuclear medium on the process of photon bremsstrahlung in nuclear collisions at low excitation energies is investigated. The in-medium nucleon-nucleon scattering T matrix is incorporated in the calculations of photon bremsstrahlung cross section for nucleon-nucleus and nucleus-nucleus scattering cases. Calculations are performed in the soft photon approximation. It is shown that the Pauli blocking of intermediate scattering states and quasiparticle energy shifts due to the mean field interaction essentially suppress the photon bremsstrahlung cross section for temperatures T≤10 MeV and densities n≤${\mathit{n}}_{\mathit{s}}$ (${\mathit{n}}_{\mathit{s}}$ being the nuclear saturation density). In the case of nucleus-nucleus collisions, when the photons are emitted from the thermalized zone, a temperature and density dependent reduction factor for the bremsstrahlung rate is calculated. It implies a typical bremsstrahlung rate which is ∼15% of that in the free scattering case.