We report on the first direct observation of the evolution with time of the vicinage effect and Coulomb explosion for H(2)(+) and H(3)(+) molecules in a thick amorphous silica layer enriched with (18)O atoms High depth resolution is achieved by using the (18)O (p,alpha)(15)N nuclear reaction narrow resonance around E(R) = 151 keV/nucleon (corresponding to a velocity V), and scanning the beam energy around E(R) The results are well described when using a Coulomb screening radius r(s) approximate to (2/pi)R(ad) where R(ad) = V/omega(p) is an adiabatic cut-off for a valence electron gas with plasmon frequency omega p approximate to 24 eV The vicinage effect is reproduced when describing the experimental energy loss function of the target valence electron gas by a single Drude function with damping factor gamma approximate to 22 eV and including multiple scattering on target nuclei (C) 2010 Elsevier B.V. All rights reserved.