The dipole response function of nuclear matter at zero and finite temperatures is investigated in an extended RPA approach by including collisional damping mechanism and coherent damping due to particle–phonon coupling. Calculations are carried out for nuclear dipole vibrations by employing the Steinwedel–Jensen model and compared with experimental results for ¹²⁰Sn and ²⁰⁸Pb.

PACS numbers: 21.60.Jz, 21.65.+f, 24.30.Cz, 25.70.Lm