Pycnonuclear reaction rates between neutron-rich nuclei L. R. Gasques a* , A. V. Afanasjev a , M. Beard a , L. C. Chamon b , P. Ring c and M. Wiescher a a Department of Physics & The Joint Institute for Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46556 b Instituto de Fisica, Universidade de S˜ ao Paulo, 05315-970, S˜ ao Paulo, Brazil c Physik-Department, Technische Universitat M¨ unchen, D-85747 Garching, Germany We present pycnonuclear reaction rate calculations for systems involving neutron-rich oxygen, neon and magnesium isotopes. The results are obtained taking into account the screening potential effects and the internuclear many-body correlations. In this work, the S-factor predictions are derived from the one-dimensional barrier penetration model. 1. Introduction Pycnonuclear reactions are of importance for nucleosynthesis at high density conditions in the deeper layers of accreting white dwarf and neutron star envelopes. Until recently the pycnonuclear reaction formalism has been developed and applied to the 12 C+ 12 C reaction in white dwarfs [1,2]. However, in the case of accreting neutron stars electron capture processes can convert the ashes of rp-process driven nucleosynthesis to neutron drip line nuclei in the carbon to magnesium range [3]. Pycnonuclear reactions between these isotopes can provide a new heat source in the neutron star crust. To model the possible consequences for the neutron star crust and to identify possible observables for such processes, the pycnonuclear reaction rates between light neutron-rich nuclei need to be determined. In this sense, the asymptotic behavior of the fusion cross section at very low energies is a critical issue for obtaining these rates. Recently, a parameter-free model for the nuclear interaction was developed based on the effects of the Pauli non-locality [4] and the fusion cross section has been obtained in the context of the barrier penetration model (BPM) [5]. In a dense metallic system, the presence of the degenerate electron gas acts to weaken the Coulomb repulsion causing an enhancement of the tunneling probability through the effective barrier [1,6–8]. Under high density conditions, the electron screening effects become so strong that the rates of nuclear reactions increase considerably even at relatively low energies. Therefore, in the pycnonuclear regime the reaction rates are more sensitive to density than to temperature. * This work was supported by The Joint Institute for Nuclear Astrophysics (JINA) NSF PHY 0216783, DoE grant DE-F05-96ER-40983, Funda¸ c˜ao de Amparo ` a Pesquisa do Estado de S˜ ao Paulo (FAPESP) and by the BMBF, Germany, under the project 06 MT 193. Nuclear Physics A 758 (2005) 134c–137c 0375-9474/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2005.05.027