Photon Strength Functions below GDER Maximum: Present Status and Outlook

Abstract

Existing experimental data on γ decay of energy levels in medium‐weight and heavy nuclei at excitation energies well above the pairing gap indicate that the role of nuclear structure effects is small and that this decay is largely governed by the extreme statistical model. Specifically, in line with the validity of Brink hypothesis and the paradigm of photon strength, the average properties of the γ decay can be described by a set of photon strength functions (PSFs) for individual multipolarities and by the level density function. PSFs are directly related to the photoabsorption cross sections σγ abs. It is well known that in the case of E1 radiation this cross section is dominated by the giant dipole electric resonance. However the size of σγ abs. and its γ‐ray energy dependence at energies below the neutron threshold are known rather poorly. In the case of higher multipolarities (M1, E2,…) the present knowledge about their roles is much worse. Available information on E1 and M1 PSFs obtained from variou...