Screening energy of the d+d reaction in an electron plasma deduced from cooperative colliding reaction

We have measured protons and tritons from the d (d,p) t reaction in liquid In, Sn, Pb and Bi during the D⁺₃ molecular deuterium beam bombardment for 15 < E < 60 keV. Observed energy spectra and yield excitation functions are anomalous and suggest that the target deuteron is also in motion. It is found that the reaction mechanism is unique to the molecular beam in such a way that one deuteron in a molecule is elastically scattered by a host metal atom and then it collides with the other to cause the d+d reaction. We call it as the cooperative colliding mechanism (CCM). Experimental data are compared with the CCM calculation and values of the screening energy of the d+d reaction are deduced. They are 380 ± 80, 570 ± 80, 670 ± 100 and 490 ± 100 eV for In, Sn, Pb and Bi, respectively. It is concluded that the screening energy of the d+d reaction in an electron plasma in metal is really large: the averaged value of 530 eV is more than ten times larger than the simple Thomas-Fermi screening prediction.