Electron screening effect in the reactions 3He(d,p)4He and d(3He,p)4He

The cross section of the reactions (3) He(d, p)(4) He and d((3) He, p)He-4 has been measured at the center-of-mass energies E = 5 to 60 keV and 10 to 40 keV, respectively. The experiments were performed to determine the magnitude of the electron screening effect leading to the respective electron-screening potential energy U-e = 219 +/-7 and 109 +/-9 eV, which are both significantly higher than the respective values from atomic physics models, U-e = 120 and 65 eV. (C) 2001 Elsevier Science B,V, All rights reserved

Energy loss of deuterons in 3He gas: a threshold effect

The energy loss of deuterons in 3He gas was measured at E d = 15 to 100 keV using the 3He pressure dependence of the 3He(d,p)4He cross-section at a given incident energy. At the highest energies, the observed energy loss is in good agreement with a standard compilation. However, with decreasing energy the experimental values drop steadily below the theoretical values and near E d = 18 keV they drop sharply (within 1 keV) reaching the domain of nuclear stopping power. This threshold behavior is due to the minimum 1s → 2s electron excitation of the He target atoms, i.e. it is a quantum effect. Some consequences are discussed