Energy loss and dissociation of 10-MeV/amu H3+ ions in carbon foils

Energy losses and fractions of H3+ and H2+ ions emerging from carbon foils of 1-8.5 μg/cm2 thickness, after incidence of 9.6-MeV/amu H3+ ions, have been measured. From the decrease of the transmitted fraction of H3+ ions with increasing foil thickness, the dissociation cross section for 9.6-MeV/amu H3+ due to the H3+-C collision has been determined to be (2.2±0.1)×10- 17 cm2. Further, the potential energy of the H2++H+ system has been derived from the energy spectra of the fragment H2+ ions, being 9.45±0.74 eV, with interproton separations being equal to those known for stable H3+ ions. For the stopping power of carbon for 9.6-MeV/amu H3+ ions a value of 83.3±5.5 eV/(μg/cm2) has been obtained from the energy-loss data. This result corresponds to an effective charge of 1.45±0.09 for H3+ in carbon. The observed stopping power and the derived effective charge agree well with the values calculated by using the first-order Born approximation.