Direct measurement of molecular breakup dynamics and vicinage effect of swift proton clusters using narrow nuclear resonance profiling

摘要

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,α)~(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≈(2/π)R_(ad) where R_(ad) = V/ω_p is an adiabatic cut-off for a valence electron gas with plasmon frequency ω_p ≈ 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 γ ≈ 22 eV and including multiple scattering on target nuclei.