Oppenheimer-Phillips effect and electron screening in d+d fusion reactions

The d(d, n)3He and d(d, p)t fusion reactions have been studied at center-of-mass energies E = 1.6 to 130 keV using intense beam currents from 30, 100, and 450 kV accelerators in combination with detectors in close and far geometry. The cross sesction ratio, R(E) = σ(d, n)/σ(d, p), approaches unity (within 2%) at low energies; thus there is no experimental evidence for the Oppenheimer-Phillips effect at subcoulomb energies. The cross sections of d(d, p)t at E ≤ 10 keV show clear evidence for electron screening effects. However, the observed cross section enhancement is significantly larger than can be accounted for from available atomic physics models. (orig.)