Inelastic energy loss of H2+ and H3+ ions correlated with molecular orientation.

Abstract

Electronic stopping power of aluminum, carbon, and krypton were calculated for energetic ${\mathrm{H}}_{2}^{+}$ and ${\mathrm{H}}_{3}^{+}$ ions together with a diproton (${2\mathrm{H}}^{+}$) and a triproton (${3\mathrm{H}}^{+}$) with specific energies ranging from 1 keV/amu to 10 MeV/amu in a frozen charge state, based on the degenerate electron-gas model and the wave-packet model. It was found that for ${\mathrm{H}}_{2}^{+}$ and ${2\mathrm{H}}^{+}$ ions a strong orientation effect can be theoretically predicted on the stopping power S and the effective charge ${\mathit{Z}}_{\mathrm{eff}}$. It was also clarified that the bound electrons significantly diminish the values of S and ${\mathit{Z}}_{\mathrm{eff}}$, and that the velocity dependence of ${\mathit{Z}}_{\mathrm{eff}}$ is considerably weaker than that expected from the existing data. The values of S and ${\mathit{Z}}_{\mathrm{eff}}$ calculated for \ensuremath{\sim}10 MeV/amu ${\mathrm{H}}_{2}^{+}$ ion incident on carbon foils are found to be in good agreement with the recent experimental data.