overlinep stopping power in hydrogen below 1 MeV and the overlinep4He metastable state.

The stopping power of H, for overlinepS was measured in the overlinep energy interval 1 keV + 120 keV using a low density gas target ( {p}/{pρ} ≈ l0 ^-3 + 10 ^-2 ÷ pρ being the Hz density at STP) with the OBELIX spectrometer at the LEAR of CEBN. Furthermore, the formation of metastable states in the overlinep 4 He interaction at rest, having a mean life of the order of 3 μs, was investigated at six target gas pressures (3 atm and 400,250,200,150,50 mbar). The influence of contaminants (like Ha, Ne, Ar, N2 and Xe) on the life of such metastable states was examined at the target gas pressure of 3 atm.