Photon Strength Function and Nuclear Level Density

Various experimental techniques can be employed to measure the electromagnetic dipole response of atomic nuclei, spanning the gamma-ray energy range from near zero up to and beyond the Giant Dipole Resonance. Historically, most measurements have been conducted at stable ion beam facilities, predominantly focusing on stable nuclei or those in close proximity. While in the past decade a limited number of measurements have ventured into regions far from stability there is a current shift in focus, as we stand at the brink of exploring nuclei in previously inaccessible areas of the nuclear chart.

This shift has been facilitated by several advancements, including the establishment of new or improved research facilities, the development of enhanced charged-particle and gamma-ray detector arrays, and the emergence of novel experimental and analytical techniques for the measurement of photon strength functions (PSFs) and nuclear level densities (NLDs) below the neutron separation energy.

In recent years, there has been a notable surge in interest in measuring the statistical properties of nuclei through PSFs and NLDs. This interest extends beyond fundamental nuclear structure or nuclear astrophysics and encompasses applications in various other fields ranging from medical isotope production, non-proliferation efforts, as well as fission and fusion reactor technologies. This growing interest across disciplines was a major motivating factor for the International Atomic Energy Agency's initiative to create and disseminate the first PSF database in 2019.