What do we really know about photon strength functions?

It is believed that decay properties of medium-weight and heavy nuclei at excitation energies above the pairing gap are not governed by structural effects but more likely by statistical properties that can be described via so-called photon strength functions (PSFs) for different multipolarities. These quantities are directly related to photoabsorption cross section (sigma(gamma)). It is well known that PSFs/sigma(gamma) are dominated by giant electric dipole resonance (GEDR) with the maximum at about 15 MeV and width of about 5 MeV. On the other hand, shapes of PSFs at the low-energy tail of GEDR are rather poorly known. Available information on PSFs for gamma-ray energies below about 10 MeV obtained from different experiments will be combined and discussed within existing models of PSFs. A special emphasis will also be devoted to possible resonance structures at low energies.