  The $^{10}$B(p,$\alpha_0$)$^7$Be bare nucleus astrophysical S(E)-factor has
been measured for the first time at energies from about 100 keV down to about 5
keV by means of the Trojan Horse Method (THM). In this energy region, the
S(E)-factor is strongly dominated by the 8.699 MeV $^{11}$C level
(J$^{\pi}$=$\frac{5}{2}$$^+$), producing an s-wave resonance centered at about
10 keV in the entrance channel. Up to now, only the high energy tail of this
resonant has been measured, while the low-energy trend is extrapolated from the
available direct data. The THM has been applied to the quasi-free
$^2$H($^{10}$B,$\alpha_0$$^7$Be)n reaction induced at a boron-beam energy of
24.5 MeV. An accurate analysis brings to the determination of the
$^{10}$B(p,$\alpha_0$)$^7$Be S(E)-factor and of the corresponding electron
screening potential $U_e$, thus giving for the first time an independent
evaluation of it.

Nuclear Experiment