Experimental level densities of atomic nuclei

TL;DR

This paper revisits the concept of nuclear level densities, showing experimental evidence that nuclei behave as constant-temperature systems rather than fermionic gases, challenging long-standing models.

Contribution

It provides experimental validation that nuclear level densities follow a constant-temperature behavior across various mass regions, revising the traditional Fermi-gas model.

Findings

Nuclei exhibit constant-temperature level density behavior

Experimental data favors the constant-temperature model over the Fermi-gas model

Behavior persists up to the neutron threshold

Abstract

It is almost 80 years since Hans Bethe described the level density as a non-interacting gas of protons and neutrons. In all these years, experimental data were interpreted within this picture of a fermionic gas. However, the renewed interest of measuring level density using various techniques calls for a revision of this description. In particular, the wealth of nuclear level densities measured with the Oslo method favors the constant-temperature level density over the Fermi-gas picture. From the basis of experimental data, we demonstrate that nuclei exhibit a constant-temperature level density behavior for all mass regions and at least up to the neutron threshold.