Photon strength function modelling, status and perspectives

The present contribution gives an overview of the photon strength function models developed to compensate for the lack of data for experimentally non-accessible nuclei. Phenomenological and microscopic approaches are presented in light of their respective strengths. Since the microscopic models included in the TALYS code are based on the quasi-particle random phase approximation (QRPA) method, the scope of application of this approach is presented. The QRPA-based strength functions, obtained using effective, covariant or Skyrme or Gogny interactions, reproduce the majority of experimental data with a variable level of precision which is briefly discussed. Some alternatives or updates to the gamma-ray strength functions based on QRPA methods are proposed. Returning to the definition of the photon strength function, particular attention is paid to the differences between the processes of photon absorption and the de-excitation of nuclei. As perspectives, preliminary theoretical results including probabilities of transition between excited states are presented.