A high-performance Fortran code to calculate spin- and parity-dependent nuclear level densities Original Research Article

A high-performance Fortran code is developed to calculate the spin- and parity-dependent shell model nuclear level densities. The algorithm is based on the extension of methods of statistical spectroscopy and implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The proton–neutron formalism is used. We have applied the method for calculating the level densities for a set of nuclei in the image-, image-, and image- model spaces. Examples of the calculations for 28Si (in the image-model space) and 64Ge (in the image-model space) are presented. To illustrate the power of the method we estimate the ground state energy of 64Ge in the larger model space image, which is not accessible to direct shell model diagonalization due to the prohibitively large dimension, by comparing with the nuclear level densities at low excitation energy calculated in the smaller model space image.