X-Ray and Bremsstrahlung Production in Nuclear Reactions

Abstract

While the role of the atomic electrons in nuclear physics has been explored thoroughly, nuclear effects on atomic interactions have remained relatively unstudied. Atomic electrons can play an important role in γ-decay (internal conversion) or beta decay (electron capture) especially when the normal nuclear decay rates are small, e.g., when they are suppressed by unfavorable selection rules or energies. Aside from providing the all-important Coulomb field, nuclei have little effect on the atom, however. Through hyperfine interactions, nuclei perturb atomic energy levels slightly (and vice versa). These interactions have been the subject of many studies. In the case of atomic collisions, nuclear interactions play no role unless the two atomic nuclei come together, a relatively unlikely process. Atomic excitation normally occurs at impact parameters of the order of the atomic or inner-shell radii, which are enormous compared with the size of the nuclei. Also, in spite of this, atomic physicists generally avoid making measurements of electron excitation cross sections or probabilities in collisions where nuclear reactions are possible. Most measurements are made with low-energy projectiles that cannot overcome the nuclear Coulomb barrier.