The role of shell model nuclear level densities for nuclear astrophysics

Precise estimation of the reaction rates necessary for an accurate prediction of stellar evolution heavily depends on the nuclear level density (NLD) model used in the calculation. In the last decade the most used reaction rates were those reported in Ref. [1], which are based on a refined version of the Fermi gas model to estimate the NLD. We developed new techniques based on nuclear statistical spectroscopy to calculate the spin and parity projected moments of the nuclear shell model Hamiltonian, which can be further used to obtain an accurate description of the nuclear level density up to about 12-15 MeV excitation energy. In the last year we made some breakthroughs in our computational methodology, by using a proton-neutron formalism and by porting our codes to massively parallel computers, which allow us to increase the speed of our calculations by many orders of magnitude, offering the opportunity to calculate shell model NLDs for a much larger class of nuclei. The reaction rates for nuclei around the waiting point nucleus ⁶⁴Ge are calculated with our shell model NLDs and compared with other NLD models available in the reaction code talys [2].