ATOMIC EFFECTS IN THE DETERMINATION OF NUCLEAR CROSS-SECTIONS OF ASTROPHYSICAL INTEREST

We discuss the relevance of electron screening on nuclear reactions between ions and neutral atoms from a few to a few-hundred keV. We present a general method of calculation of the atomic effects and discuss quantitatively the limiting cases of low and high velocity of the nuclei as compared to typical electron velocities. Results for several low-energy fusion reactions and proton capture processes are presented and recent experimental data on the d3He reaction are discussed. Concerning this latter reaction, the reported rise of the astrophysical factor at keV energies cannot be explained in terms of electron screening and should be connected with a nuclear-structure effect. © 1990.