NUCLEAR-LEVEL DENSITIES INCLUDING THERMAL AND QUANTAL FLUCTUATIONS

The nuclear level density for solvable model Hamiltonians is calculated as a function of the excitation energy, taking into account both large-amplitude thermal and small-amplitude quantal fluctuations. The formalism, which is applied to simple systems displaying a phase transition (deformed to spherical, superfluid to normal) as a function of the temperature, accurately reproduces the exact solutions. The contribution of thermal fluctuations changes the level density by an order of magnitude. Quantal fluctuations are essential to reproduce the absolute energies of the system and thus to relate the excitation energy to temperature. © 1990 The American Physical Society.