Energy loss and dissociation of 10-MeV/amuH3+ions in carbon foils

Energy losses and fractions of ${\mathrm{H}}_3^{+}$ and ${\mathrm{H}}_2^{+}$ ions emerging from carbon foils of 1–8.5 μg/${\mathrm{cm}}^2$ thickness, after incidence of 9.6-MeV/amu ${\mathrm{H}}_3^{+}$ ions, have been measured. From the decrease of the transmitted fraction of ${\mathrm{H}}_3^{+}$ ions with increasing foil thickness, the dissociation cross section for 9.6-MeV/amu ${\mathrm{H}}_3^{+}$ due to the ${\mathrm{H}}_3^{+}$-C collision has been determined to be (2.2±0.1)×${10}^{\mathrm{-}17}$ ${\mathrm{cm}}^2$. Further, the potential energy of the ${\mathrm{H}}_2^{+}$+${\mathrm{H}}^{+}$ system has been derived from the energy spectra of the fragment ${\mathrm{H}}_2^{+}$ ions, being 9.45±0.74 eV, with interproton separations being equal to those known for stable ${\mathrm{H}}_3^{+}$ ions. For the stopping power of carbon for 9.6-MeV/amu ${\mathrm{H}}_3^{+}$ ions a value of 83.3±5.5 eV/(μg/${\mathrm{cm}}^2$) has been obtained from the energy-loss data. This result corresponds to an effective charge of 1.45±0.09 for ${\mathrm{H}}_3^{+}$ in carbon. The observed stopping power and the derived effective charge agree well with the values calculated by using the first-order Born approximation.