Electron screening in $d(d,p)t$ for deuterated metals: temperature dependence

The electron screening effect in the $d(d,p)t$ reaction has been studied at the Ruhr-Universit\"at Bochum for most of the metals and some insulators/semiconductors by using deuterated targets [1]. The deuterated targets were produced via implantation of low-energy deuterons. As compared to measurements performed with a gaseous $D_2$ target, a large effect has been observed for all metals. In particular work has been done to investigate the high solubility for the metals of groups 3 and 4 and the lanthanides, at a sample temperature $T=200 ^{\circ}$C. The hydrogen solubility in the samples dropped to a level of few percent (compared to $T=20 ^{\circ}$C) and a large screening became thus observable. An explanation of the large effect in metals is provided by the plasma model of Debye applied to the quasi-free metallic electrons. A first evidence of the validity of Debye's model is that the deduced number of free electrons per metallic atom agrees with the calculated number from the Hall coefficient [2], for all metals investigated. A critical test of the classical Debye model is the temperature dependence $U_e \propto T^{-1/2}$. \newline [1]F.Raiola et al.: Eur. Phys. J.A19(2004)283; \newline [2]C.M.Hurd: ``The Hall effect in metals and alloys''; (Plenum Press, 1972).