Nuclear level density and related physics

¹ Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory/Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824-1321 USA
² Department of Physics, Grand Valley State University, Allendale, Michigan 49504 USA

^* e-mail: zelevins@nscl.msu.edu ^** e-mail: karampso@gvsu.edu

Published online: 14 November 2018

Abstract

The knowledge of the level density as a function of excitation energy and nuclear spin is necessary for the description of nuclear reactions and in many applied areas. We discuss the level density problem as a part of the general understanding of mesoscopic systems with strong interactions. The underlying physics is that of quantum chaos and thermalization which allows one to use statistical methods avoiding full diagonalization. The resulting level density is well described by the constant temperature model in agreement with experimental data. We discuss the effective temperature parameter and show that it is not related to the pairing phase transition being analogous to the limiting temperature in particle physics. Other aspects of underlying physics include the collective enhancement of the level density, random coupling of individual spins and the role of incoherent collision-like interactions.